Just speaking from my personal experience and observations, my general impression is that men who feel threatened by or take a judgmental stance toward feminism both: (1) don't understand it, because they cannot or will not take the time to try to understand it, and (2) appear to be emotionally stunted and have had some experience or set of experiences that have made them hateful, fearful or distrustful of women.
I understand both problems (the first is an extension of the second), but as a matter of personal ethics, I refuse to offer excuses for adults acting like overgrown adolescents, nor do I enable it.
A man understands feminism and why it's a thing. Period.