I'm not sure which is worse - liking all modern art because one is supposed to like it, or hating all modern art because one is supposed to hate it.

I think both are equally bad, to be honest, but that the latter is less common than the former. I think that people, given enough exposure to a diverse selection of some medium or some category, will eventually come to like at least a section of it. The widespread hatred of "modern X" is probably more often down to ignorance than signalling. Most of the signalling that goes on here is from people trying to demonstrate how hip they are; familiarity with current art is good for the image they are trying to promote. I think anti-modern signalling is largely from people who are trying to prove how conservative or old-fashioned they are, as a way of reinforcing other parts of their image.

That said, I move in circles that are more artistic than academic, so this is an obvious way in which my results could be skewed.