That's somewhat true (in my 9 years there, I never saw a yield on green for left hand turn, which never made sense to me)...
However, just because (as some have argued) everybody does it or has done it...does not make it legal or right. We have all probably broke the speed limit and park where we shouldn't...is it legal or right? Let's not be lemmings here.
The reason a lot of people do it...like a lot of laws, it is not enforced. Plus, how many of us read or remember all of the rules of the road outlined in the drivers handbook?
For example, if you are on an interstate...multi-lane...in a construction zone...each lane is separated by a SOLID while line instead of a typical dotted line...do you guys know what that means or is implied? How about the difference between a solid and dotted line?
But think about it this way...if you are sitting out there in the middle of the intersection...left turn yield on green...traffic to your left and right have the red light...you are waiting for a clearing to turn. All of sudden some drunk or deranged driver ignores the red light and crosses the intersection...BAM! Ok, it is his/her fault...but was it worth it to be doing what everyone else does?
Anyway, like I said earlier, I believe the other guy should have been ticketed as well. You suppose to approach the yellow with 'caution'...gunning it is not being cautious.