Even if you believe they should for one reason or another, it simply isn't the case. Feminist anti-FGM efforts have had a lot of success. But they don't care about other GM. Even if they believe male circumcision is bad, they think FGM is worse, and if you bring up MGM, they'll accuse you of derailing the conversation. The stickied posts on our subreddit explain why this is wrong. On the other hand, many men's rights activists are in denial about circumcision, and dismiss the issue. On basically every r/MensRights post about intactivism, there are always detractors, but they thankfully get downvoted. Also, some MRAs tend to downplay FGM, instead of clearly laying out why and how all GM is harmful and why it should be stopped.
They can't get over their egos for one fucking minute and care about the people being hurt. Millions of people are mutilated every year, many of whom are babies or kids, and some of them die, too.
This post lists examples of feminists who lean either way.
https://www.reddit.com/r/MensRights/comments/8q7x0d/conference_the_fragile_phallus_warning_postmodern/
https://www.reddit.com/r/AskFeminists/comments/22pfce/should_feminism_take_a_more/The comments on this aren't so bad, but look at the comment at the bottom.
https://www.reddit.com/r/AskFeminists/comments/kci127/thoughts_on_intactivists/
https://www.reddit.com/r/AskFeminists/comments/3aphc3/how_can_we_forge_or_strengthen_the_bond_between/
https://www.reddit.com/r/Feminism/comments/w77d7/new_intactivist_activism_subreddit_created/
https://www.reddit.com/r/AskFeminists/comments/7h89s4/is_it_bad_for_me_to_be_an_intactivist_someone/
https://www.reddit.com/r/AskFeminists/comments/8ua4h9/can_you_be_a_feminist_and_pro_circumcision/
https://www.reddit.com/r/AskFeminists/comments/1pgdf9/circumcision_activism_circumcisionism/
https://www.reddit.com/r/AskFeminists/comments/kjm31a/why_do_intactivists_and_anti_fgm_activists_argue/
https://www.reddit.com/r/AskFeminists/comments/1tjhmw/why_dont_feminists_do_more_to_discourage_male/
https://www.reddit.com/r/AskFeminists/comments/27x4yv/can_you_understand_why_this_kind_of_article_makes/
https://www.reddit.com/r/AskFeminists/comments/ymnw0/why_is_it_all_my_body_my_choice_but_that_gets/
You're an intactivist if you're an intactivist. Being a feminist or an MRA doesn't make you more likely to agree with intactivism. In practice, most of them aren't intactivists, and they don't grasp the full scope of intactivism. Intactivism should be egalitarian.
there doesn't seem to be anything here