The Supreme Court on Tuesday appeared to be leaning against a program in Boston in which the city raises the flag of third-party groups outside City Hall to promote diversity and other messages but declined to fly a Christian flag. Boston argued that the flags on its flagpole are government speech and that city officials may choose the messages they want to convey. Justices questioned whether the city relinquished control of that message by approving just about every other request to fly a flag except for the one made by the religious group in 2017.