Anybody shocked or outraged by this clearly doesn't know the stance of the ACLU. They've helped protect the free speech of Westboro Baptist and actual Nazis organizing actual Nazi marches before. And I wouldn't have it any other way really. They protect shitheads just as much as the rest of us as long as everyone involved is within an equal legal framework.
If the government and society was ever was completely overrun by say, a bunch of fundies that think Atheist or "evolutionist" people posting ads, holding rallies, or whatever was hatred against Christianity the ACLU would (and should) protect us from overreach.
The only time that there should be intervention is if it gets violent or someone encourages other people to commit acts of violence against innocents or political opposition like there has been recently in Charlottesville with that White Nationalist who ran people over and the night before that when the rest of his gang started punching the people counter-protesting.