As far as Pool having a few 'characters' in it, that really isnt different than any other sport. Look at Tennis for example. For the most part you have the average athelete competing. But how about John Macenroe? I think he could actually give lessons to Strickland.
As far as some of the threads of people losing their temper and going to the extreme? I've only been on the boards for a month or two, but I have seen a few pretty impressive hostile threads. For the most part they all seem over money. Either a bet not payed, a sale gone wrong, or a product not matching its description. If people started making custom hockey sticks worth thousands of dollars, or promoting side bets of hockey games on those forums, I bet the level of arguments would drastically rise.
On the subject of the avatars? That is just what different moderators allow. Some have very strict rules on what they allow, some like AZ has a fairly open policy. Personally I have had to close threads as I tend to read these forums form work, and some of the graphics don't meet my companies policies. Does that make the poster wrong? not at all, I should just read that post at home is all.