Why do people feel the need to continue to refer to gays as "p*does"?

I keep coming across stupid people (in person and online) who love to refer to gay men as p*does. (Not directed at me, just used in a general blanket statement - or towards celebs).

Why is this? What's the best way to deal with that? Go off on them, educate them or just ignore them?

It's so damaging not only to the community but to us as gay individuals.

Thoughts?