because Thomas Edison loved a good ass-kicking

I'm inclined to agree with QT, although I might broaden his definition of violence.

With the exception of ballet, which is not exactly a populist medium, and some bits of television, cinema is the only artform exclusively about motion. Cinema is about the image, movement within the image, and movement from image-to-image. (Cinema is also about the passage of time, but we'll ignore that for now.)

Cinema is also a narrative / dramatic artform, which means it is about conflict, crisis, tension, resolution, growth, etc. The easiest way to achieve conflict, crisis, etc. through an artform based on images and motion is by using images and motion, and the easiest way to achieve that is through violence and action.

Most romantic comedies are bad because White People Talking is not cinematic; problems solved by talking may be healthy for society but they ain't much to look at. They aren't visual.

It's not impossible to make a non-violent movie visual, it's just rare. We treasure movies like "Annie Hall," "Eternal Sunshine of the Spotless Mind," "Two for the Road," and "Eyes Wide Shut" because they tell their romances visually. But maybe they aren't so non-violent after all: one could argue that the non-chronological editing of "Annie," "Spotless," and "Road" is so jarring as to be a form of violence.

"8 1/2" doesn't begin with Guido saying "I feel so trapped! Sometimes I wish I could escape, but then real life pulls me back in!" That's poor cinema. Instead, it shows him be suffocated in his own car (violence), then climbing out the top (action), flying away (action), then being flown as a kite over a beach (action), until he is pulled cruelly out of the sky and crashes into the ocean (violence).

If someone's not chomping at the bit to see "Bright Star," it's not because he doesn't like poetry but because White People In Costume Reciting Poetry doesn't make good cinema. An actor reciting Keats for two hours does not make good cinema anymore than writing Keats on a canvas makes a good painting. (But from what I understand Campion has attempted to make "Bright Star" as visual as possible, and I applaud her daring.)

Most romantic comedies are bad because White People Talking is not cinematic . . .

By your definition of cinema, though, it is. If scenes in romantic comedies simply consisted of pointing a camera at a conversation and never moving it, you might have an argument. But a substantial amount of montage goes into even the simplest conversation, creating cinematic motion. Even the motion from a close-up to a wide shot is a significant change of perspective, and in close-up, the movement of an eyebrow can be as significant as a car crash. The fact that we're mostly unconscious of the cinematic grammar of these scenes anymore does not mean it's not there.

Furthermore, most of those conversations, even in the most dreadfully predictable examples of that genre, are staged in settings with significant visual interest: Italian villas, stunning cityscapes, fancy restaurants, or those Nancy Meyers Pottery Barn fantasy homes that make our esteemed reviewer-in-chief retch.

So, the White People Talking (or Any People Talking) are doing so within the precise definition you've set down for what constitutes "cinema." Whether or not it's "good" cinema is more a matter of your personal taste.