There's a scene halfway through "Bad Moms," wherein a PTA meeting full of suburban moms turns into a full-on frat house-style rager. Moms in sweater sets, khakis and sensible sneakers chug liquor straight from the bottle, make out, huff whippets, crash tricycles and urinate on lawns, all in glorious slow motion, hair and spittle flying to a pulsing pop beat.