I haven’t really run into any so I’m not sure what you mean?  Is there something different with them versus a normal feminist?  Because to me, feminism means being for equality for EVERYONE.  Feminist (myself included) aren’t out to make the world dominated by women, which is what I think the stereotype is: that we hate men, and we are out to destroy them.  I suppose these are called extreme feminists or… something?  

But that’s not what we want.  That’s not what feminism is about.  

We want equality for everyone.  Everyone should have the same rights regardless of gender, race, sexuality, and everything else  :)    

We’re also not out to tell women how they should live.  I’ve seen some posts of groups like, going to fashion shows and messing with the models to spread their message and no, that’s not what feminism is.  We’re for EQUALITY and CHOICE!  A woman has a CHOICE in what she wants to do. If she wants to stay at home and be married and have children, fine.  If she wants to go out and work, that’s fine too.  Both of these are fine as long as it’s her decision.  I don’t have any right to go to a woman and say, “Gasp, you should be working, don’t let this world oppress you by staying home,” when she WANTS to stay home.  Hell, I want to stay home and write and craft and cosplay and have dinner ready for my wifey.  That’s the choice I’m making, that doesn’t make me less of a woman. 

So… if a tumblr feminist is someone who believes in equality for all and choice, then I’m cool with that.  But if it’s someone who is harmful towards a group to reach their goal, then no, I’m not cool with that.