I didn't get to see the play live, and the video online is a tad choppy, but I'm not so sure the end result of the first goal being ruled out is wrong. I think the linesman flagged Magee for offside, which was clearly wrong, but wasn't the first LA player to touch the ball offside, thus negating anything that happened afterwords?
At least that's my take from watching the mlssoccer.com video. Since everyone seems to be in agreement that the call was wrong though, I have a hunch there may have been a New England player on the line or something else that I'm missing.
Edit: Heh. Just realized the non-goal I've been scrutinizing is not the one everyone is saying was wrongly ruled out. Well then.