Because of Burfict's body of work.
He has a history both in college and he pros of this kind of behavior.
Remember when he was twisting ankles after he whistle during a game against Carolina?
Even the Ravens called him out for his dirty play.
In Saturday's game alone he:
1.Attempted to stomp on Ramon Foster's foot after the whistle.
2.Left the bench to engage Steelers after the Shazier hit on Bernard.
3.Gave Ben an extra knee to the shoulder on his sack, after the whistle.
4.Layed out Brown with a hit to the helmet that was way more vicious than Beckham on Norman.
5.He was in official's faces all night and at times the Bengal coaches were trying to contain him because even the sideline reporter was saying that he was out of control.
Burfict isn't a passionate player that just got caught up in the moment, he has a history of dirty play and out of control behavior.
BTW, if you look it up you can find a video of Pacman Jones taking Amari Cooper to the ground, ripping his helmet off, and then slamming Cooper's head into his own helmet in the Bengals/Raiders game this year.
Couple of real class acts...