Because they can believe space wizards but the idea of a twin sister of one of the most powerful space wizards in the canon being able to also learn space wizard shit over the course of several intervening decades breaks their incel brains.

Same reason why Holdo caught shit for not telling Poe anything while my Navy friends were all relieved to find out she wasn't the kind of ship commander who would actually fucking execute you and dump your body in the drink for the level of blatant insubordination that idiot was pulling just in front of her face nevermind scheming behind her back with Finn and Rey to undermine her plans, and also to accuse her of being the traitor and arranging a kangaroo court mutinee basically acting as a thin veneer for him to shoot her in the face under color of "law" for having the gall to actually treat him like the insubordinate demoted twit he was.