Welcome to the solipsistic world of equality activism, in which the removal of sloganeering in chalk on the pavement, which might have been wiped away by routine maintenance, if rain didn’t get it first, is equated with the censorship of a faculty artist.
Read Franklin Einspruch 's superb piece When Artists Fear their Audience here.
I think there's a current confusion in the world left of center that needs some distinction: There is a huge difference between a "liberal" and a "leftist."
Liberals generally embrace diversity, discussions amongst different opinions and points of view, protection of our basic rights, and an open, receptive ear to all.
Leftists, on the other hand, are generally aligned with the Marxist dogma that prohibits all but one voice and seeks to silence all others and endorses only the "approved" form of art. Some of the biggest mass murderers in modern history (Hitler, Stalin, Mao, Pol Pot, Castro) have all been leftists.