Wow, I really don't understand this hatred towards Kenny...to me he is a bro. The choices you make decide how he acts towards you, if you support him he's cool, if not then...well he acts like you'd expect him to. For example, when Larry wants Duck to be killed 'cause he thinks he's been bitten, siding with Larry is basically saying Duck should die. Why would Kenny forgive you on that? Lilly's reactions are normally worse than his (stressy from the word go) at least Kenny is a friend all the way through, unless you disagree with him. Kenny also wants to help people (Ben and co in episode 2) but Lilly flips 'cause of it.
Even though I think the meat freezer bit is over the top, when it comes to Kenny's loyalty, it still makes sense. If Larry became a zombie, everyone would be at risk. Hell, Kenny is probably thinking that Larry would kill them all and then there would've been no way for him to save Katjaa and Duck. TBH, I tried to save Larry in my first playthrough, but as soon as I found out that he died anyway (and the fact that it majorly annoyed Kenny), I did it all again just to side with Kenny. I liked him from the beginning...first impressions are important; he wanted to help you, and he was friendly, but Larry and Lilly wanted you to be left to die.
And Kenny isn't a coward. Firstly, when it comes to saving Shawn...imagine it, the outbreak has only recently begun and you haven't had much experience with zombies, saving a stranger would be nothing compared to saving your own son. Kenny is prepared to die for Duck, he's not a coward just because he's not prepared to die for a stranger. Secondly, if you help him kill Larry, he goes badass when you're trying to stop Danny; he goes against a guy with a gun to save you, his friend. And that's why he doesn't help you if you don't kill Larry, the friendship is questionable and, therefore, he would've found it harder to help you.
His reaction to Ben saying everything was his fault was understandable, he had put everyone at risk, betrayed them and indirectly caused the deaths of Katjaa and Duck. Hell, even Lee can get pissed at him (even threaten him) for that which shows just how bad it actually was. In my game he even warned Ben not to say anything to Kenny...so Kenny isn't really overreacting.
Just saying...Kenny is AWESOME