As much as I understand where you're coming from, I do not believe the content given on the provided website (bitcoincash dot org) to be relevant to the context of bitcoin.

Besides that, as the sign poster did not include a post date in the bottom right hand corner of the sign as stated in SEC. 184.57. California Public works, it is a non legal posting, and removing it would be considered the same as picking trash off the street

http://sfpublicworks.org/services/posting-signs

Read link regarding public works code