Basically, how many warnings before you're put in the Dunce Corner? I've blown up a ton of personal vehicles lately, mostly out of malice but sometimes for fun, and had the "Bad Sport Warning" pop up about 7 or 8 times, but still not been relegated to Bad Sport.
I tried to get a tank driver into the bad sport server by driving close to him with my most expensive vehicles...he destroyed my PV at least 12 times within half an hour...ignoring all the other PVs he was destroying I was shocked he didn't get removed for bad sportsmanship.
One of the guys on here insists that you can earn counteracting "good sport" points by completing lots of jobs. I've blown up my fair share of player vehicles, and so far I've been Clean, but I also run a crap ton of contact missions (even after the pay nerf), so maybe he's right.
The secret to life is honesty and fair dealing. If you can fake that, you've got it made.