waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!
Seriously. Get some thicker skin. Family Guy is hilarious. Like South Park, they make fun of EVERYONE and EVERYTHING. Because of this - one in awhile they make fun of something that you like.
Doesnt mean you have to rush out and express your outrage on the interweb.
And yes - there was a Family Guy where after the crash of civilization of 2000, Peter founds a new city around an old Twinkie factory. He later makes guns out of their irrigation pipes. The people throw them out and burn the guns. Just then, Mutant Stewies attack! "Get the guns, they are our only hope!"
And yeah - the Simpsons had something similar - they got rid of all their guns, only to have the ghosts of Billy the kid and friends come back and terrorize them all.
Anyway. The moral of the story is - if you watch shows that make fun of as manythings as Family Guy, you need to either not watch, because your psyche is too delicate, or laugh at yourself and know that on the next show they will make fun of gays and jews.
That or start your letter writing campaign - but that FG episode is like 4 years old at least.