Wrong....the worst mass murder since 1917 has been at the hands of leftists......there is no check to their ability to murder people...
Russian leftists....25 million murdered.
Chinese leftists....over 70 million murdered.
Cambodian leftists, over 1/3 of their population murdered......
And you would then have to define what you consider extremists on the American Right...since the American Right isn't the same as the "Right" in Europe or around the world, which is really simply one set of leftists ...
The American Right believes in the Constitution and the Bill of Rights....individual Freedom and a limited government....you don't get to mass graves with those beliefs....
Believing that government should have more and more power, and that individuals getting in the way of that power keeps the government from doing "good things," the way the leftists do...is how you get to mass graves...they think checks and balances, and the separation of powers.....used to limit the accumulation of murderous power in the hands of government....are wrong and need to be removed....
The American Right believes the exact opposite....so no...the extremists are not the same..