I don't think that anyone would dispute that management has the "right" to enter your room (not sure about the legal case cited). Management probably has the "right" to do a lot of things that violate basic guest expectations or reasonable service standards.

Violating DND is one of my biggest pet peeves. As with so many things, the Caesars policy that "we will check every room every day" is an overreaction and/or just for show in response to the Vegas tragedy. Given the facts the OP cited, I doubt that this was someone enforcing any policy but rather either sloppiness or worse on the part of the staff. He is right to complain.

I guess Flyertalk has evolved over the years. No one is screaming, "compensation!!!!"