Exposing Vigilantes
One great thing about 70's crime dramas is they were basically realistic. Often, vigilante types are more criminal than the people they go after, as evidenced in this Dirty Harry installment.
Vigilantism makes a perfect smoke screen for truly dangerous people. They are not all sane like Dirty Harry is.
"Dark Night of the Scarecrow" also points this out clearly.
"I had to rescue a burning baby. See, I got burning baby all over me."
- CHEECH