Ugh, I hope the artist doesn't read that, since I think could be bad to read such comments about your work. Personally, I've been insulted in every possible way, but I have my Zen way of dealing with it, also known as "I don't give a f..."
Joking, as you know I appreciate constructive critics and even insults if AT LEAST they point out something wrong in the game! Saying "art is ugly" is an opinion and very subjective IMHO, since I know a lot of people follow that artist on tumblr.
But anyway, in the end what matters it's how the game does. The game is doing well, so they can say what they want about the art, writing, gameplay, whatever!