I have a question about Facebook ettiquette -

I'm part of a 'private group' or whatever they're called on Facebook where a group of like-minded people share stories and pictures related to feminism and social justice. Today, somebody posted a picture of a naked woman with most of the shot focused on her pubes with the caption "Eat out more often".

This is TOTALLY not safe for work and in lots of other social situations and I mentioned, pretty politely that this was NSFW and would it be possible to keep full frontal nudity off the group page. The woman who posted it seemed to get upset at my request and said it was really an empowering message and that she would not stop. Then she posted another pic about cunnilingus. I reported the pic to the group admin (I have no idea who it is) and now am feeling kind of badly.

Am I an asshole? Pics like these have never shown up the group's feed before and I'm not quite ready to leave the group entirely as I've found lots of great strangers and articles here but now I feel like a prude.

ETA:

Turns out it was the group admin who posted the pic and the group's description has changed to 'some pictures may be NSFW'. Turns out that it's a super empowering picture I guess and I'm most likely going to have to leave. Nevermind. "Feminism is for Everyone" means "Feminism is for Everyone who enjoys unexpected porn at inappropriate times".

ETA 2: Also, I'm kicked out of the group. Whatever. I'm more hurt than I probably should be.