I've been blocked by a lesbian even though I made it clear that I have nothing against lesbians but I'm not one myself.

On the one hand, that's certainly not a good reason for someone to block you. On the other, I don't suppose the person blocking you needs a reason. But I suppose something about you or something in your profile must have wound them up. Could it be that they were attracted by your profile pic but were frustrated that you aren't into women?