The penalty for all crimes in the U.S is too lenient.
I believe its the only way to decrease crime. Raise the stakes.
Either the fear of the penalty will deter them, or the fact they are locked up dead (death penalty) will 100% reduce crime.
Asking people to be nice, carrying signs, Facebook posts where people write "can't we just all get along/behave/etc" won't help. Neither will asking people to be better parents. "Come on, be a better parent!" posts on Facebook are seen often, but don't help. The people that are good parents, don't need the message and the ones that need the message aren't going to change their ways because someone asked.
Much stricter penalties are needed.