Yes, that is true. People kill other people regardless of race, religion, creed, ethnicity, gender. And if a person is not included in that group they also kill other people.
Knives are used to kill people more than handguns and far more than rifles. Cars have been used to kill more people (mostly accidentally but sometimes on purpose) than any other weapon.
So you're correct that people kill people and the tool that is used can be anything including bare hands.
However, the left is so full of hatred and so vile these days they have taken to killing people so much so that all of the mass shootings in America are leftists. A much smaller percentage is just some whacked out psycho doesn't kill out of political motivation but some other craziness going on in their head. After then are Muslims terrorists. I think I heard about 1 conservative nutjob who killed a few people a while ago but by and large conservatives, libertarians, constitutionalists and so on do not kill people. All politically motivated mass shootings or other politically motivated killings are done by leftists. All of them.
And THAT is what this meme is all about.