I think its kinda dumb to say all bars are bad places... That's kinda like saying all people who concealed carry just wana shoot someone. A few bad apples ruin it for everyone.
Some bars are great, some bars are full of 'uncool' people. Find one that you and your friends can enjoy, but returning to bars where you have repeatedly had problems isn't the smartest idea. And sometimes the difference between a good experience at a bar and a bad one isn't where you go, but when you go...
As for defusing belligerent people, unfortunately not much works on drunks as far as I can tell. I haven't read it myself (its on my wish list), but apparently
Verbal Judo makes for a good read...