From Libertarian Michael A. LaFerrara:
No one is suggesting that displays can’t be built and funded on private property by private funds, and displayed to the public. But using public property, which is theoretically owned by everyone, and taxpayer funds effectively forces people to sanction and pay for religious ideas they may not agree with.
And if a Christian display is allowed, shouldn’t Muslim displays also be allowed? Or atheist displays? Or anyone with conscientious beliefs of any kind? We’d all be fighting for our own piece of government property, and access to our neighbors’ wallets. We’d have a free-for-all, effectively politicizing private beliefs. Isn’t this precisely what the First Amendment’s implied “Wall of Separation between Church and State” is intended to protect us against?
We can only guess what Jefferson would think about the Bladensburg cross. But it is hard to believe he would sanction taking money from private citizens to pay for it.