A hippy-dippy woman open to making love as a spiritual gesture or exercise can quickly lose interest when the recipient of her largesse starts talking crudely about slamming ham, etc. Watching this kind of prolonged miscommunication isn’t the least bit funny. There’s never been a 30something married guy (which Paul Rudd is playing) who’s ever been this clueless. Not on this planet. Which is why the scene just lies there.
Because the idea isn’t to be “funny” but to make a point that stodgy married guys are too thick or slow-witted to betray their wives even when the “other woman” has openly invited their attentions. This is roughly the same idea used by Hall Pass, that glumly unfunny Owen Wilson-Jason Sudekis film. Married guys don’t have a clue when it comes to cheating so don’t worry, girls! Strictly a sop.