The only real asexual people, are those who, because of a physical condition, do not have, no can develop, sexual desires even if they wanted to.
You can consciously decide you're never going to have sex, but that's not really being asexual. You can also consciously decide to have sex with a person of your same gender, even if you don't really feel any attraction, but that doesn't make you gay.
There are real asexuals, and real gay people. There also are people who label themselves as such and behave as such, but in reality aren't.