Acknowledging that we're on a bit of a tangent, I'd say that no matter how relatively frequent or infrequent these cases are, if any of them manage to restrict free speech, they are VERY consequential. And in fact, sometimes they succeed in restricting speech.
I think it's very important since we're trying to assert 'a large chunk' or 'many' feminists. I'm not seeing evidence of that. Only a few fringe cases which are also largely misinterpreted. As is the angle of 'free speech.' Too often I hear claims of free speech violations when talking about private facilities, websites or venues which are not in any way protected by free speech. If RF decides that you can't talk in detail about rape because they consider it obscene it's not a 'free speech' issue because you're not entitled to not be moderated by RF, only by government oversight. And in certain public settings where space is being rented, leased, or set aside for a specific purpose or program, the organizers also have a right to moderate the content that happens there. i.e. you go to a public school room being used for a chess club and say 'Chess sucks, Go is way better.' Them having you leave is not a violation of your free speech.
I believe that many western feminists are ignorant of their Muslim sisters' plight.
Really, are you asking why such ignorance is relevant? Did I misunderstand your question?
I don't believe that. Near every feminist in organizations, social events and conventions I've been to have read books by Muslim women on the subject, at the very least some of Fatima Mernissi's work or Malala Yousafza's. Let alone the number of symposiums, signings and general debates over the subject at large. Once again, are you sure you're not classifying feminism by a minority of young people on tumblr? Because that seems to be what's getting the lion share of attention and then called 'feminism.'
I'm also seeing 'the plight of their Muslim sisters' used either as a scapegoat against Islam in general (which neither of those two prolific Muslim writers did) or as a sort of misdirection off addressing domestic social issues in a sort of 'but there are starving children in Africa' kind of way.