Besides, since when was it forbidden to mix emotions? There's plenty of worthwhile humor in the best movies in many genres -- horror, action, romance, drama, you name it. And the best comedies have moments of seriousness. Really good stories run us through a gamut of emotions.
Exactly. Some of my favorite movies don't just work the same emotional nerve over and over again, but embrace several different modes and tones--all at the same time.
WITNESS is a crime thriller, love story, culture-clash story, with plenty of humor, suspense, action, and romance.
THE WICKER MAN is a paranoid thriller, horror film, black comedy, and musical.
THE STUNT MAN is a twisty psychological suspense piece, a slapstick action-comedy, a mystery, a love story, a backstage drama, a playful examination of illusion versus reality, a political allegory, etc.