If you read some people’s social media feeds, you might think that all police officers are racists. They’re not! I know that for a fact! This is one example (and a very blatant one) of assigning the shortcomings of one individual to everyone in a particular group. What if we did that to everybody? Would you like that if it happened to you? 
Do you know any teachers who have committed any vile acts? Does that mean that all teachers are like that? Of course not! Do you know any preachers who have behaved in highly inappropriate ways? Does that mean that all preachers are like that? Of course not!
Every individual person is his own person! I thank God for every police officer, every teacher and every preacher I have known! Are they perfect? Certainly not! But each person deserves to be treated as I would like to be treated (Matt. 7:12), and every person deserves the benefit of the doubt (1 Cor. 13:4-7), as much as I want them to give the same to me!