Just because Twitter has the right to do something doesn't make it right for them to do it. And that they have the right to do it also doesn't mean that people shouldn't be angry at them for having done it, or use their right to call them out for it. Twitter shouldn't be doing this stuff. You totally can defend their right to do it while damning their actually doing it... but that isn't what you are doing as the person you are arguing with didn't even claim they shouldn't be allowed to do it: they merely said they shouldn't do it.