I will defend him on this:

Calling a religious extremist an extremist hardly smears the entire religious group.

It should not, but it does.

In people's minds, over a billion Muslims are responsible for 9/11 (not 20 something hijackers). Over a billion Catholics are responsible for Church Molestations (not a limited number of perps - and that's even assuming non-consent, of which I have never been convinced). A hundred million Evangelicals in the USA are responsible for hatred on gays (not a limited number of their leaders). And so on.

So yes, I do accept the argument that using the word "feminazi" to refer to a feminist who is not simultaneously a Nazi (eg, April Gaede is a feminazi, and for a time her daughters were) smears all feminists.

That said, it remains true that there is no ultimately agreed upon term to refer to woman supremacists that excludes gender egalitarian classical feminism. So, as long as it doesn't exist, it's Markaba who has to bear that we call "feminist" those who call themselves "feminists". Not unlike you have to bear with the association of your religion with the most unsavory elements thereof.