You might want to think about this a little bit more than
murder=bad people
bad people=should be dead
First of all, there is no possible way to have a 100% correct conviction rate for criminal cases, meaning that automatically you are executing atleast a handful of innocent people, and that's with a fantastically accurate judicial system. Second of all, this opens up a Pandora's box of bad possibilities. Does this mean that extrajudicial killings are now ok, as long as the man killed killed someone else? What if gang member A killed gang member B, then was killed in revenge? Gang member A's gang might see his killing as murder, and pursue "justice", which leads to an unending circle of violence. My point being, one mans justice is another mans murder.
This idea isn't just unpopular, it's stupid and dangerous.