I make Bleeding Kansas as the kick off to the democrats party being a party of violence. Would anyone propose an earlier starting point? Of course their resistance to Reconstruction, then Jim Crow, were violent, but it took the injection of modern socialist/ Marxist ideology to really turbocharge their violence
https://en.m.wikipedia.org/wiki/Bleeding_Kansas
It began at the very foundation of the Democrat party and reached its first violence in May of 1838 with Marti Van Buren and the Cherokee Indian resettlement known as the Trail of tears.