@xj9 In theory under ideal conditions proprietary software could be morally ok. Someone could write it without backdoors or antifeatures and in a way which treats users fairly. In practice though whether proprietary software is screwing you over or not is usually unverifiable.

Increasingly over time though proprietary software has become more egregiously immoral and simply a tool of social control or for extracting rents, and as a software developer I've seen that from the inside. The unethical aspects of proprietary development which I could see going on was one of the main factors which lead me to start using GNU/Linux in the early 2000s.