I've seen so many people call the Kenny character a dick, or a dumbass.
Kenny won't be your friend at the beginning of the game if you choose to throw his son outside for being bitten. If you don't do this there's still a chance to be his friend, if you side with him at all times and feed his son. That's a pretty fair bargain, considering Duck should be fed because he's a child and Kenny's argument is basically siding with you anyway.
Anything after this, you have to give Kenny a break. His entire family died, not to mention he gets over it in about two days. He can lash out at you but he's going through the toughest experience of anyone in the group.