I find this statement kind of ironic. I believe the true definition of "Man Up" is to do what you want, and fuck what anyone else thinks about you. But usually a statement like "Man Up", especially from BP and women means "You're doing something that conflicts my values, so I'm going to say "man up" to shame you to go back to being a sheep and following order and ideology of society"

By going MGTOW and having some conflicting values that don't fit in with what people want you to be, to question the status quo and determine a rational course of action, THAT'S manning up.