I do believe that piracy is moral and ethical and sharing knowledge is what helps humanity thrive. However, due to copyright law, the sharing of knowledge is criminalized. Private trackers serve as a way for people to share knowledge with less of a risk of bad actors (commonly known as copyright trolls) interfering. Private trackers very much are a "secret club", but that is why they are able to stay open for long periods of time without legal action. For me, whenever I download something from a private tracker I am also sure to share it publicly on other P2P networks, as to not gatekeep.