That would be discrimination.

Even if that was supposed to be humor, it was one of the most ignorant comments I have ever heard.

Since it's obvious you don't understand the word you used, let's show you a definition:

dis·crim·i·na·tion (n).

1 - The act of discriminating.
2 - The ability or power to see or make fine distinctions; discernment.
3 - Treatment or consideration based on class or category rather than individual merit; partiality or prejudice: (ex. racial discrimination; discrimination against foreigners. )

You may want to note number three as especially meaningful here. Whether or not you like it, it's still discrimination even if the person isn't like you. And yes, even if they're gay.