“Fundamentally, however, its goal is to secure the dignity and well-being of all women. How could any self-respecting man be against that?”
It’s a fair question, but your logic is flawed. You conclude on the basis of your premise (regarding the goal of feminism) that “most men are insecure and feel threatened by sharing power with women as equals” (i.e. lacking in self respect), but it doesn’t occur to you to question the voracity of your premise, or more importantly, whether others accept it as unquestioningly as you do. How ever much you believe it to be true, and no matter how misguided you think others are for rejecting what you believe to be true, it is quite possible for self-respecting individuals to reject something that they see in a different light to you. Wouldn’t you agree? And since only a minority amongst adult populations in western democracies declares support for feminism (around 17%) then the remainder (who reject it) must consist of both men and women, rendering your reasoning rather hollow, as you’re only applying it to men.
This approach to an issue, arguing from an inflexible premise as if others accept it, is zealous and manipulative and reminiscent of religious fundamentalism. And when feminists argue in this way, trying to diguise abuse and manipulation as logic (and failing), then this is how feminism presents itself, as manipulative fanaticism. Now why wouldn’t self-respecting individuals be against that?