I think following rules of etiquette are all well and good...and I think for the most part everyone on the PGA Tour follow them...that said, the PGA Tour is a business and there's lots of money involved. Golf for these guys is not something they necessarily do for fun with their friends...in ALL SPORTS people get angry with themselves, and with their opponents...it is called competition. When you add money to the competition equation I think some people, such as Tiger, will openly display less than ideal behavior. Considering, in every sport I can think off, this less than ideal behavior often ends in a fist fight, golf is doing quite well!