I'd file a formal complaint, so that the documentation supports the next guy. I'd sue, to shore up the slippery slope. If the OP had resisted, he'd be dead or hurt & in jail.
Somebody draws a loaded gun with 1 in the chamber, takes the safety off, and points it at my center of mass, that person is threatening to execute me. Cop, BG, doesn't matter who he is. As a corollary, somebody giving orders with confidence born from being armed and having an armed partner, that person is implictly threatening me with force. I may not comply because you're an officer, but I'd darn well better comply because of the gun, nightstick, taser, and boot.
Where there is a legal requirement to obey the orders of a police officer, the police officers must be held to a strict standard regarding the orders they give. Where police officers are allowed to use threat of deadily force to ensure compliance, they must be held to a strict standard regarding the use and threat of deadily force.