How funny are jokes involving retards to you?

If a joke is funny, I laugh at it, subject matter doesn't matter to me.

Upon thinking about it, I find I do call people retarded a lot.

Lots of times I'll say retread (as in, re-tread a tire) instead of retard.

Once I saw this big goofy oaf of a guy call his brother or friend, whoever it was, a 'stoopit retart'. So I say that sometimes too, I found it pretty funny.