People either like men, like women, like both to some degree, or like neither. Each of these four concepts can be and is summarized and communicated symbolically with a word, whether "straight," "gay," "bisexual," or "asexual." This verbal and written symbolism to represent ideas and concepts is called language. It's very big in Europe.
There are two sexes, and only so many combinations of what does and does not sexually attract a person. We should all be who we are, and we should own it, not put our heads in the sand. If a man is sexually interested in other men, he isn't straight; he is either gay or bi. There can be a lot of variety in exactly where on the spectrum he is, but everyone is something. I know it's cool to do the "labels are for soup cans" thing, but let's be honest and keep our feet on the ground.