What part of public vs private
does skeptic not understand? The Christian guy who carries a big Jesus sign on my campus has a right to express himself as long as he does not get so loud that he disturbs the classes. This is a public institution, but his freedom of speech is protected. There are also currently some religious anti-abortion guys on campus holding giant signs with really horrible photos supposedly of dismembered fetuses. They also have freedom of speech rights, just as I have the right to look away from their signs.
Now, if our coatless bearded friend tries to erect a permanent Jesus sign
on campus, he will get into trouble. Not because of a hatred of Christians (that is clearly not the case since probably a majority of the students and staff here are Christian and he is welcome to stand here all day in the cold with his Jesus sign, talking to anyone he wants to) but because this is a public (state funded) school
There are private religious colleges, like Georgetown (a Catholic Jesuit university) that have lots of religious statues and signs and so forth. Those are private property and if they want to put up permanent religious symbols and signs
they are free to do so. It is their property to do with as they wish. Likewise, if some group tried to put up a permanent religious-related sign in a private shopping mall it would be taken down if the owner did not want it there.
If someone puts up a permanent religion-related sign, symbol or statue in a public city park, it should be taken down, even if it is pretty, even if I agree with it because it promotes something I believe in. Because it is public space, not private space. It is against the law to put religious stuff there. Religious people and atheists alike should be willing to abide by the law.