The Bill of Rights was added to protect us from the Federal govt. First amendment rights do not apply in a private forum.
You can ban any message in your home even.
“Experience should teach us to be most on our guard to protect liberty when the Government’s purposes are beneficent. Men born to freedom are naturally alert to repel invasion of their liberty by evil-minded rulers. The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding.” — James Madison