The U.S. Supreme Court seems likely to rule in Shurtleff v. Boston that Boston established a public forum in allowing third parties to fly flags at city hall and therefore could not prevent a Christian group from flying their flag. Banning the Christian flag would constitute viewpoint discrimination. The justices suggested that the city could ban all flags and stay within their constitutional rights. (Bloomberg Law, January 18, 2022, by Kimberly Strawbridge Robinson)
When the government speaks for itself, it does not have to include other viewpoints but when it creates a public forum, it cannot discriminate based on viewpoint. (Vox, January 16, 2022, by Ian Millhiser)
A Jewish legal advocate and a Baptist minister argue that Boston should be able to ban the Christian flag given the importance of church-state separation. The city should not appear to endorse religious messages by flying a Christian flag. (msn, January 16, by Rachel Laser and Brian Kaylor in The Boston Globe)