The movie Howl helped me to understand a role art can play in the politics of regulation. Art done well can have a very high status, a status which transfers to the actions used to create or express this art, as well as to the actions depicted by the art. And by making some examples of an action high status, one reduces political support for regulations limiting such actions.
For example, since most folks are uncomfortable with explicit sexual conversation in public, obscenity laws limit such public conversation. But when artists create high quality and hence high status art with explicit sexual discussion, people are reluctant to let obscenity laws apply to it. So they’ll either have to make an exception in obscenity law for high status art, which will lead to many disputes since art evaluation can be subjective, or they’ll have to just allow a lot more public obscenity. Similarly, having high status art depicting homosexuality, being created by them, reduces support for laws against homosexuality.
Of course this can also work the other way – high quality art that presents a low opinion of an example of some type of action can raise support for regulations limiting such actions. So the power of art isn’t only a libertarian power – it is a power of status, which can be directed toward many ends. But since art is an expression, it will more often conflict with laws forbidding expressions than with other sorts of laws, and so will tend to push for freer expression.
So does art tends to be a force for political good? Well if you favor freer expression, you’ll think so. But beyond that, it depends on the taste and judgment of the artists, relative to the many other forces pushing for more or less regulation. I suppose I’ll give artists the benefit of the doubt, and assume they helps a little, just as I’ll presume all other sources help a little on average. But it would sure be nice to get better data to make a more refined judgment.