A police officer, quite literally, cannot afford to lose his temper as did Officer Sharlow.  Of course Bumpis was being a "jerk."  He was arrested for being a jerk, should you expect him to be a gentleman as he awaited placement in jail?  Sharlow "blew it" big time and, because of his actions, he will suffer professionally, the other officers present who didn't intervene and, instead, supported Sharlow will suffer professionally, and the City will likely pay a sizeable settlement to Bumpis.  

Security cameras, body cams, dash cams and bystanders with cellphone cameras should convince officers that foolish, abusive behavior toward prisoners or the public is a very bad idea.  Sharlow learned this the very hard way.