I've always wondered why people get so upset when others say "I'm lagging".
I just got done with a 
game. My ping was 35, all of a sudden it went to 130-150 and was there for the rest of the game. I told my teammates and they said "You're not lagging, you're just shit" after I got hit buy a couple 
Q's I couldn't tumble out of because of the delay. I don't get it.
It is mainly due to people not being understanding. Personally, I tend to be more sympathetic towards people having lag issues because I have had to deal with having a consistent 1,200 ping. (Satellite internet, woohoo!) At the same time, however, people who are lagging and choose to continue to play knowing that they are not going to be able to play at their full potential should not be surprised when people become upset, especially if you are beginning to feed or just under-performing in general. I can see both sides. I would just say that we all need to try to be more understanding.
THe other problem, is that no one can see you ping....so if you ARE bad, (not saying you, just as an example) then its easy to call lag, and shove off the blame. So, since people do that a lot, people tend to call bullshit when someone is actually lagging.
