The malicious/abusive parts of nonfree software are almost always tied to it's updatability. Avoiding updatable nonfree software prevents users from entering into an abusive relationship with a nonfree software vendor. https://www.gnu.org/proprietary/proprietary.en.html, 550 instances of malicious functionalities, I'd bet all instances are for software where the vendor can update it.

Your argument is like "Banning guns will incentivize people to use knives, people who want to only ban guns for violence sake are hypocrites." There is a kernel of truth, but it's really just ignoring the bigger reality.