Sure its possible, each antimalware vendor makes their own decision as to what is detected as malicious by their software. Its possible for them to detect whatever they want. Whether they actually start to detect pirated software will probably depend on their relationships with the software vendors and how their customers react to such things.
Questions about ethics are always very subjective, and Im sure the point could be argued either way. Personally my opinion on the matter is I don't want software I use to do anything other than what I got it for. i only want antimalware software to detect legitimate malware, and I don't want it trying to enforce copyright or anti piracy restrictions. If I want that functionality I will get software that is designed to do that.



