Garbage Disposal?

Ok, so, Thad and I have been having an argument about what you can and can't put down the garbage disposal since oh, about five years. He basically thinks NOTHING should go done the disposal while I've always been of the mindset that if it's any kind of wet food, done, no brainer. SOOOO, I was cleaning the kitchen the other day for Thad (which is NOT my typical job), I hate touching any kind of nasty dishes or leftover meat, so this was a magnanimous gesture on my part. Anyway, I dumped two large tupperwares, one full of shredded chicken and one of chili. Now, listen, I didn't just shove it all down at once, I did it little by little so as not to overwhelm the mechanism. Well, I'm down to the last little bit of chicken (ALL of the chili is long gone) when the water starts to back up in the sink. CRAP. Thad shows up a few minutes later and I tell him what I've done and he immediately launches into a tirade about how you aren't supposed to put anything down the disposal. I'm thinking, well what's the damn purpose of the stupid thing if it can't gobble down a little leftover chicken? Long story short, we had to call the drain guy who shows ups and spends, no lie, TWO HOURS unclogging the stupid thing. The unfortunate part here is the diagnosis from the drain guy "I found a thick sludge clogging the pipes". Dang. So now Thad's convinced he's right and I'm stuck with having to throw food in the trash as opposed to down the drain. So here's my question....what is the damn thing for????