This sort of thinking is lazy and dangerous. Police are people first. With that said, the type of person who is attracted to law enforcement is more likely to be the type of person who enjoys power over people, but as shown by the Stanford Prison experiment, even nice people can turn into sadists when put in a position of power over others. Some cops are pricks, because some people are pricks. Some cops are good people, because... some people are good people.

Be smart, be respectful, be careful, be thoughtful, but don't get so lazy as to start stereotyping all people of a certain type... I believe there's a word for that, but I bigot forgot what it was.