Security guards and private citizens kill criminals every day as well.
...cold-blood murder in the vast majority of cases...
I doubt it.
Police often kill suspected criminals for doing little or nothing wrong. Often police kill people for not following orders fast enough, even though the people do not even understand what is going on.
Does Obama really support this? Well, he sure isn't even suggesting doing anything about it.
Often there are many ways of subduing a person other than outright killing him. People have rights, and their rights are to have a jury trial when accused, not to be executed "Judge Dredd" style.
What good is law if rights are not upheld? The people are getting sick of this. They are starting to take matters into their own hands as we see in various riots. When they go a little farther, it will be with armament that even the cops won't be able to withstand.
Is this what we really want? Get the police to back off before they turn America into a real anarchy.