The KKK was Democrats, not Republicans. You might want to review some history there.
Also, McVeigh and Nichols worked alone on their revenge plot, as is typical of the Right. Two guys working in secret who come up with a very effective terrorist attack. On the Left, it's the mob. Hundreds or even thousands of jackasses in the streets committing low grade violence, typically, graffiti, smashing windows, general property damage, injuring dozens often innocent bystanders, looting, toss in some amateur arson, and general pubescent mayhem.
It's the Left that likes to send threatening letters, SWAT people with false 911 calls, and harass them in a juvenile-like fashion.