Mansplaining is a sexist term.

This can be easily demonstrated by the fact that the exact same response made by a woman would not be considered mansplaining, even if the same objections to the response remain. This negates the very concept of sexual equality.

It's a way of dismissing someone's response by highlighting their sex. That's sexist.

You could just state your (potentially valid) objection to their response without bringing attention to their sex. That wouldn't be sexist.

I'm certainly not perfect and often struggle with communication, but it's pretty hard to keep up with the arbitrary standards for men these days. I don't know what using terms like this is supposed to achieve, but it sure seems counterproductive to me, especially when used against men who defend equality for women.

Good luck with this tactic.