Defending himself against what, a fan who was stood behind him being pushed into him because of the melee. Yeah fuck that piece of shit fan :fp:
It's hardly stupid to defend yourself particulary if your getting hit in the ribs which someone was doing.
I question how many people are defending Punk just because it's Punk. If it were someone like Randy Orton in this situation, I wonder how many would be calling for his head. At the end of the day, Punk messed up. At any wrestling event, there are bound to be drunken idiots and if you put yourself in that situation, the only person to blame is yourself. Punk's been in the business how long? He knows better. Luckily for him, it didn't turn out any worse than it was.
There is a difference between Punk and Orton though. This is Punk's first indiscretion that I have heard of so it is uncharacteristic of him. Orton has had many, many incidents and so this would have been Orton once again doing something that a top star shouldn't do.
As you said though Punk has been in the business for long enough and should know that you don't hit fans no matter how idiotic they are being.