They are because they are for a particular kind of policy issue, rather than an orientation. They defend all speech regardless of current policy.
Then again, feminists are based on an issue to. They are only liberal because the status quo is masculine in nature. Though feminists are not one organization like the ACLU, so it's hard to explain them as a monolith. Some feminists from the 70s probably support the status quo now.
On individual issues I tend to side with the ACLU and "liberal feminists" (as opposed to "socialist" or the pinnacle of insanity "radical feminists"). That is because I think that the issues would be resolved to my ideological liking if they got their way. There is no point in reforming what you don't feel needs reform. It's only when saying everything is fine or some issues need to go backward that you become conservative.

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