I dropped that point because who knows? The meaning and interpretation of the law you cited vs the authority of the city county council is really a matter for the courts, not INGO'ers. I don't know enough about street murals and the law to know if there are any precedents.
Oh, I think there are ample precedents. The courts have often weighed in on the matter of protected political speech and the constitutionally required impartiality of the government in regulating political speech. Whether those decisions are all controlling on Indianapolis, who knows. That said, I present for consideration:
https://www.washingtonpost.com/nation/2020/07/22/california-blm-maga-art/
https://www.washingtontimes.com/news/2020/jul/1/dc-sued-over-black-lives-matter-painted-city-stree/