They have done something horrific, and apologizing and pretending to regret it (or even sincerely regretting it) will never undo what they did.

Would the MeToo movement promote Bill Cosby as an ally if he apologized and said he regretted raping women?

Would the abolitionist movement have promoted former slaveowners as allies if they apologized and said they regretted enslaving their fellow man? (though at least you can free a slave, you can't undo inflicting genital mutilation upon your son)

No amount of protesting/advocacy from them can ever make right what they did, or ever make it up to their son.

What they should be doing is accepted that they screwed up beyond repair, and just staying quiet and try to have as little involvement in their son's life as possible, since their choice to genitally mutilate him shows they haven't the faintest clue what is good for him.

It's time to make Intactivism into a movement of genital mutilation survivors, not a movement that accepts genital mutilators.