I would tell them to Get back on the horse they came in on. They have no claim that the monument cannot exist, there is no sponsorship of state religion (lol) and if someone is offended by the monument they should be told to " Get over it".
This group has done similar things here in the past and they get their knickers into a wad at the drop of a hat.
On anthor line of thought, I am thinking of going to Hastings to hassle Kinky Friedman during his book signing; it would be nice to see some Lubbock FReepers there to hassle the git.