It’s best to explain why what’s your doing is not mansplaining. That always works.

If somebody accuses you of mansplaining, there is nothing you can do. that makes this so toxic as an argument. It's basically saying "Whatever you are saying or want to say is worthless because of your gender". I know that mansplaining is in theory a specific kind of disrespectful explaining, but in too many cases it's used to deflect valid arguments. If someone is acting like that, the only way is to not interact further.