Yeah, it's all relative, to some degree or another. One famous American extremist was John Brown, who resorted to extreme methods in a failed attempt to end slavery. But as it turned out, violent military force was how slavery was ended. So in John Brown's case, he was right, but it was "the wrong execution of the right idea."
But some might say that Brown was still wrong, since he didn't work within the system, as a good moderate would do. He could have waited a few years, and he would have been able to fight on the Union side in the Civil War.
Nowadays, the battle lines are drawn a bit differently, yet there still seems to be some sort of impasse over various issues. Neither side seems willing to budge; there is little willingness to negotiate in good faith or make any kind of compromise. That leaves very little room for moderate proposals.