Virtually all of the violence comes from the right. They are angry and have always been. They know it too, that's why every time there's a shooting they immediately point to the left, making up bullshit evidence collected from internet trolls.
Right wingers were always angry. They were angry when they came back from Vietnam and felt abandoned by the government, and formed white supremacist terrorist groups like the Order. All of this is well documented. Proud Boys is an offshoot of that nonsense.
Of course all this anger culminated in the bombing of the Murrah building in OKC. But it didn't stop there. Nearly all mass shootings in the last 25 years were committed by right wingers. It's not a secret they are easy to agitate.