I don't understand why I don't like this part of my job?

Yes. Sometimes good people go to jail, I'll be the first one to admit it. There are some situations where we HAVE to make arrests, regardless of our personal feelings about it. Discretion only allows us so much before we are mandated to do certain things. Other times, I'm happy as hell that a particular person is going to jail, because they deserve it. They're street trash, and have no business being out and about, causing hate and discontent.