I don't really think you're disagreeing. If Twitter wants to promote free expression, which I would think of as supporting the ideal of free speech, then they s

I don't really think you're disagreeing. If Twitter wants to promote free expression, which I would think of as supporting the ideal of free speech, then they shouldn't ban Trump. If Twitter wants to ban Trump then they are in conflict with the ideal of free speech, or in your terms they aren't promoting freedom of expression by banning Trump. Twitter has claimed in their own promotional material to support free expression, so it may be a bit disingenuous for you to suggest they may not want to promote free expression.