It seems that you don't think that all of the negative messaging about men and masculinity could have a bad affect on men and their mental health
It could harm a man's mental health, but I just don't know what harms it would do. I don't know the facts, so I'm not speaking on that. Besides, if your claim is true, wouldn't all the negative messaging about women produced by sexists harm the mental health of women even more?
(or you add in some kind of whataboutism,
I think such arguments are acceptable in this context because women really do face worse problem than men. They certainly face worse issues than just men saying mean things about them.
or it doesn't matter because that's not what feminism really is...
Why would women acting shitty and misandristic be a part of feminism?
or that this could even be a concern worth taking seriously
No, I take it seriously. It's just I think this is largely a matter of messaging. So yes, feminists should change their messaging toward men. But men should promote feminine culture, and I argue this is a more substantive issue than just one of presentation.
I also kind of feel like we're getting into "No Real Scotsman" territory or something similar.
I don't see how that's true. I've dealt with a number of examples, and I've frequently conceded that people such as you have presented legitimate counter-examples. Can you give an example of an argument of mine that falls victim to this fallacy?