So, while the brains of most sexually mature men will discover that female anatomy causes uncontrolled erections, urges and erotic thoughts about copulation, -a percentage of those men will also experience the same reactions when viewing male anatomy due to the persistence of the default brain wiring from early in the womb. This is NOT a moral weakness. It's a society-bonding empathetic strength and it is the MALE-MAJORITY experience. Human nature does not change and once upon a time - a culture in Greece completely acknowledged these facts and openly integrated them into everyday life. In ancient Greece - everyone matter-of-factly (yawn) knew that men were wired like this and there was no stigma whatsoever regarding men who loved men (AnalSex NEVER being a component of these M/M relationships). It is well known historically that the greatest love in the life of Alexander-the-Great was general Hephaestion! And as I said - human nature does not change. What the Greeks commonly knew - is still true.
See, higher brain functions such as reasoning, logical thought & volition are not what makes sexual orientation happen. Sexuality is a result of merely recognizing reflexes and the results of a man's internal sexual wiring. This is why people can't "choose" their sexual orientations. It's not a force of will-power. It's pure discovery and the reasons "why" are completely outside of a person's control.
There is also a secondary reason why men who don't necessarily see men as physically desirable are still able to enjoy sexual release with certain men. See, male human sexuality is reflexive because our genitals are exposed and erections are caused by a number of factors - not just erotic thoughts. External stimulation (friction/masturbation) is one cause. And this is often what men who fall onto the lower numbers of Kinsey's scale discover. So, what causes Kinsey 1's, & 2's to happen? Sexual release with these guys is usually caused by (2) factors:
The 1st is activity that causes an erection reflex. This can be many things but when with another guy it's usually activity that brings both men into close contact (such as wrestling) and the physical interactions cause repeated pressure and friction on the genitals of the man as he interacts. Depending on how the nerves in the spinal cord deal with the signals coming from the genital area will determine if the guy experiences an erection. This is literally beyond his control. He experiences the event. It is a reflex. But once this reflex begins, it also causes a feedback loop based on blood-chemistry to occur. The blood entering a man's penis is trapped there because return circulation is partially prevented (this is what physically causes the man's penis to grow & harden). The blood trapped in the penis is soon depleted of oxygen which causes the color of a mans erection to turn bluish as time passes. To prevent injury, the tissues inside and near the penis release protective potassium ions which cause a number of things to occur - including the release of a large number of neurotransmitters in and around the erection that make the event feel very, very, very good. The purpose of this release of neurotransmitters is prevent priapism & simply to move the process along to completion (orgasm) -after which, the blood flow will return to normal. This is why erections caused by friction over an extended period feel good ... and why once a man's penis has taken on a hard-blue hue that he often feels an urgent desire to orgasm/ejaculate.
The 2nd component to this - is the level of trust and emotional comfort the guy shares with the other man (-minus any negative social messages that may be present that would form psychological inhibitions). The overall aggregate "score" these interactions create determines how willing the guy is to letting the event causing his penile-pleasure to continue. So, even if the man himself does not find other guy physically erotic, - he may be willing to allow an erection that has resulted from a friction-reflex linger in order to enjoy the experience - especially if the other man is a trusted friend who does not mind the event -or- is experiencing a similar event himself. When those dynamics come into play, it's not unusual for either or both men to ramp up the activity that is causing the genital-stimulation in order to enjoy the next reflex: Ejaculation (which feels good beyond words). The combination of these activities also produce the neurotransmitter oxytocin - that causes each man's brain to create stronger emotional attachments to his buddy. It makes for a more solid friendship bond that feels more "trustworthy". And once this trust is established, -men will get together for physical intimacy & sexual release more frequently - especially when a guy who is low on Kinsey's scale finds himself outside of a M/F relationship & is sexually on edge - needing to climax to regain his mental/emotional equilibrium. Why jack off when it feels so much better to have a best-buddy do it? That's what puts the "best" in the term "best-friends".
So, there are (2) primary contributing reasons for male sexual bonding and every combination of intimate friendship results based on the unique combinations of perspective both men have. This ranges from: "I'm not into the male physique erotically, but having a trusted buddy jack me off feels much better than doing the deed myself (for the same reasons it's harder to tickle yourself than for someone else to)"; -All the way to the other: "I think the male physique is beautiful & desirable and I really enjoy giving another guy intense pleasure because it's where my loving, emotional & erotic core is naturally.".
Author & Sexuality Researcher P. Tremblay wrote in a related research paper that: "In 1960, I was growing up in a working class environment where male homosexual activity was the rule, not the exception. Its predominant manifestation was "sex with equality," thus including mutual masturbation and oral sex, but not anal sex (Bagley, 1997, p. 183). The latter was not even thought about, except for eventually learning that passive anal sex was an activity engaged in by apparently degraded males who thought themselves to be like women, or were labeled as such because they were accepting the status of being anally penetrated. As for ourselves living in a world where effeminate males did not exist, our sexual activities with other males generally reflected our social relationships: most sex with one's best friend, and lesser sex with lesser friends. We also had girlfriends and knew what was to be done sexually with them as it was so well understood via having learned the word "fuck" and its clear meaning. This explains why even the thought of "fucking" one's best friend was precluded: the activity or related desires was in violation of our equality based male bonding friendships. Sexual activity was also only a small part of our daily activities, and it was not an everyday activity although, at times, it was enjoyed more than once a day... (In Ref to any Suicide Ideations) My own adolescent environment, however, precluded having such feelings (of depression) because desires to have sex with other males, and engaging in such joyful activities, resulted only in knowing that I was part of a majority even if, as with masturbation, my sexual activities with other males were to be private acts. It is also doubtful, given the information available from Ancient Greece, that adolescents boys of (that) period would have experienced self-hatred and isolation, with associated suicidal feelings, because they had love and sex desires for older males. If suicidal feeling existed, they would likely have been experienced by a male youth who was being ignored by all older males.(!) Therefore, the reported exceptionally high rate of "suicide problems" for present-day males recognizing their same-gender sexual desires (males who often identify as gay or bisexual) may be a social construction intimately linked to another possible social construction: the increasing rarity of males reporting same-gender sexual desires and related sexual activity in the Western World."
And it's for many of these reasons that explain why most guys are amBIsexual to some degree and also why so many men are unaware of the widespread nature of these common feelings and experiences!