I'm a huge fan of King of the Hill. And I think Bobby is a crucial part to the show, I mean he's the total opposite of what you would think the son of Hank would be. It allows for more story options and ultimately a larger range in episode variety. He is a key member, just as everyone else is. You got a psycho (dale), a ladies man (boomhauer), a guy that gets shat on all the time (Bill), arrogance (peggy), conservative guy that seems just like my dad (Hank), hottness/cheater (Nancy), hottness/idiot ditz (Luanne), minority/homewrecker (John Redcorn), minorities to contrast vast differences (Khan, Mihn, and Kahn Jr.), I could go on and on and on.
Every character has something different to offer, and the purpose is to extend the possibilities of what can happen. I wouldn't give anybody up.
But I have to agree that the pig episode was both creepy and just incredibly bad. The guy gets chopped up, so Peggy and Luanne just go home? Weirrrrd.
But there are many many great episodes. One of my favorites is when Kahn Jr. got her first period, and after Hank thumbs through his first aid handbook he asks her if she knows how to tie a turnicate.
Little things like that just make the show very entertaining.