Whenver I play FFA they usually win unless I kill them, but honestly it's a hassle. I have to essentially stop caring about everyone except 2 people and make it my mission to run around the map just to kill them. It's not only annoying but as long as the people boosting are smart and do it somewhere hidden, they always win. People ruining one of the only fun game types makes me angry.
Why they do it for headshots and such, I don't know. You get headshots naturally, just play the game for a bit and you'll get your stuff. On the other hand, if they just went into a challenge lobby, it would affect absolutely no one, and why do people get flamed for that? So someone got all the camos and stuff, you know they cheated, why do you care? People get called every name in the book just because they have everything. Maybe they don't want to take a year out of their life to get everything the right way. In the end, it doesn't affect you at all, so I just don't see what the problem is.