If you're sexually attracted as a man to another man or as a woman to another woman, you are as straight as the Pisa tower.
If you idolise another man as a man or another woman as a woman, be it for their personality or their body, but no sexual attraction is involved, it's basically extended jealousy or aspiration.
Anyone who says you can be straight and want to suck another dude's **** is probably a weirdo that will start to shout about the 'spectrum' before you say hello.