Marshall calls Robin a "slut"

When she sleeps with the naked man (mitch) but he never says anything like that to Barney. Ik there's no word male equivalent to slut, there's pervert.

But isn't it out of character for marshall to behave like that?

Ted sleeps with tons of women too. When ted says he hasn't been laid for 5 months they behave like that's horrible.

Barney is a hypocrite so that would sorta make sense BUT How can the nicest dude on the show marshall call only robin that word!!!!