This is a video of Moto2 racer Romano Fenati blatantly pulling the brake lever of another rider mid-race. For the record, that is frowned upon. Probably even scowled upon while waving a no-no finger. Thankfully, Romano's attempted sabotage (which scored him a black flag for irresponsible driving) didn't end with a crash, although I wouldn't be surprised if it did end with someone from his opponent's team waiting to greet his legs with a tire iron. The ol' pleasure to make your acquaintance.
Keep going for the video.
Thanks to Mark FS, who agrees that's not safe.