I think the funniest thing to do is just follow them around.
I was playing Dom a few days ago and the final killcam of the match was a couple of boosters. It showed the guy shoot the other guy in the head, then the guy does his tac insert respawn, sets another tac insert, gets shot in the head.
They immediatly left, but I continued to follow them for 3-4 games until they just logged off. They were whining and crying at me the whole time, but I could just laugh and laugh. A lot of fun.
If I find them, I make it my personal mission to annoy them for the rest of the game. After the game ends, I report them both. I've only had one game so far where I wasn't able to find the boosters. I had to go into Elite to find where they were boosting. I make sure to check that building near A Dom on Mirage every time now.