Hmm... Okay...
Some men are attracted solely to men. (sounds an awful lot like homosexual/gay)
Some women are attracted solely to women. (sounds an awful lot like homosexual/lesbian)
Some men are attracted solely to women. (sounds an awful lot like heterosexual/straight)
Some women are attracted solely to men. (sounds an awful lot like heterosexual/straight)
Some people are attracted to both men and women. (sounds an awful lot like bisexual)
All people have the ability to acknowledge that a person of the sex they are not attracted to have physically appealing qualities, so a man attracted to solely to men is capable of discerning whether or not a woman is physically appealing. This ability does not alter the fact that the man attracted to other men is, in fact, attracted solely to men. It only acknowledges that he possesses the sense of sight and ability of reason. Hence, the term homosexual or gay most certainly still applies to him because he does not have a desire to be with said female in either sexual or romantic terms. Similarly, a person who is attracted to both males and females, regardless of capacity of attraction towards which, is rather well described as being bisexual.
The fact is, while these terms may be labels, they also serve incredibly well to describe who we are as sexual and romantic beings and, most importantly, they describe the overwhelming majority of human kind. Are there outliers? Of course. Such is the nature of, well, nature. Perhaps I'm oversimplifying because I'm not, according to you, as complex of a person as you are (very arrogant statement and one without very much basis at all, by the way). The point is, if you're a man and you like other men, but not women, the label gay works well. If you like men AND women, even if you like one more than the other, you're bisexual. Because there are only 2 sexes (not genders, as sex is a biological descriptor that can only be changed through complicated surgery and even then only to a certain extent, and gender is social and can be quite flexible) the issue is not nearly as complicated as people enjoy trying to make it.