If we were to put a monument of Shariah law on the capitol grounds, would that be permissible as well?
No, it wouldn't.
http://www.washingtontimes.com/news/2013/aug/20/kansas-public-school-promotes-5-pillars-islam/
Parents are fine with this school having a painting of The Last Supper, but became upset when Islamic displays were put up.
Hypocrisy at its finest. Those who support the 10 Commandments on state property are the first to scream, "If you don't like it, don't look at it!". Yet, when it's their turn to utilize that advice, it's a no go!