There's no excuse for vandalizing the sign.

However, I believe that displays on government property which are either pro- or anti-religion is unconstitutional. As long as Wisconsin issues permits (which, by the way, seems to me to be a form of selling indulgences) for religious opinions on public property, then the possibility of symbolic "martyrdom" of minorities remains. I think that's the point, and offhand, I'd guess that the goal of the FFRF is to drive it home and close off evasive loopholes. All such displays belong on private property.

Mac