the previous owner of the property SOLD it to us.
free dixie,sw
I hadn't seen that the people who wanted to post something on that sign owned it. I also haven't seen that the posters of the message own the land. If they do own both the sign and the land it is on (as opposed to leasing the land), then I don't see how anyone has any legal standing to challenge the sign that they want to post.
If there is a lease involved, then the issue becomes what the terms of the lease are.
In checking back to the original article, it says the railroad owns the land, not the SCV. What rights that may or may not give them regarding the contents of a sign that is on their land I don't know. There may be some language in the contract that the owner of the sign signed with the owner of the land that allows the landowner some control over the contents of the sign.