Once I was blond, now I'm bald ;^)
What makes a rightwing extremist? Answer with a question for you, what makes a leftwing extremist?
Rightwing extremists hold republicans responsible for not doing enough. Rightwing extremists threaten to take their vote and stay home. Rightwing extremists rant a lot. Rightwing extremists appear to want government minding every aspect of the citizenry's lives. Rightwing extremists use the Bible as taliban'ers use the koran. Rightwing extremists display intolerance. Rightwing extremists advocate extreme measures, punishments, etc. Rightwing extremist believe that because they are on the fringe that they are in the lead. Rightwing extremists establish a caricature which the MSM and the left easily use to taint the middleground impression of the conservative viewpoint. Does that address your question?
bald counts! LOL just kidding...
Off the top of my head I would say a leftwing extremist is anti-gun ownership, pro-abortion, pro homosexual marriage,anti death penalty, big government.
There are liberals who basically take their vote and go home, and rant, and use atheism to the extreme that God should not be mentioned in public,they also rant (example James Carville, Howard Dean). Leftwingers can be guilty of the same things that you put down as being characteristic of right wingers.
It seems to me that it is the moral issues and constitutional issues that separate the liberals from the conservatives. For example the current filibuster issue.