Smile. You have First Amendment rights, too. At least for the time being.
Instead of crying and moaning about other people’s free expression and demanding to have it taken down, why not pick up your own paintbrush?
They have a 1st Amendment right to create it yet their are a few questions here worth debating. Is porn protected free speech? Yes, yet their are limits to such protections. Children are brought to this museum and they should be protected from this. If consenting adults wish to view it, fine yet it should not be allowed in the public square.