Sure there's creativity in writing a Chuck Close filter, or a Monet filter, or a van Gogh filter: they're all conceivable and likely to become popular.
The problem is that it's not polite and indeed somewhat aggressive to put forward a bit of code as an equivalent to the human brain. Remember it's the artist's brain that's the object of interest here, as much as any well-understood but beautiful flower or pebble. Since the brain is the most complex object we know of, it's fair for anyone to feel insulted when something they create intuitively, using their whole personality, is imitated using a few lines of code. It's really a dilution of their personal "trademark" output, to frame it in commercial terms.
In a court of law, you can't do various frivolous/cheeky things without risking being found in contempt of court.
Society as a whole isn't so different, and Feynman is not a good guide to civilized, socially conscious behaviour. Remember the time he got someone seriously injured because he wanted to unmask a perpetual motion hoax? http://hoaxes.org/comments/papparticle2.html
It might have been an innocent act on Feynman's part, but bear in mind that he was just trying to expose the guy for his own slightly arrogant satisfaction. Not a good look when that ends in serious injuries.
Also, "What do you care what other people think?", the title of one of the entertaining Feynman books... Well, going back to the issue of trademark dilution, actually, in civilized society, you know as well as I do that considering other people's feelings and livelihoods is crucially important. It's not merely a conventional matter of piety, deference or respect, although sometimes those things are appropriate. It is a question of humility.
(That might not be a very HN sentiment because having a conscience gets in the way of disruption.)