We all know tech companies can do what they want, they've been doing it from day one. But consistency is a desirable trait for a lot of reasons, not just for fairness or equality but also because it allows one to make predictions about what content will or will not be allowed.
Twitter may be their own company but we all know how large of an influence they are for public discourse, including important public and private conversations such as that between politicians and the citizens of their country, so suggesting that there cannot be an issue because there are no laws being violated is shotrt-sighted. As a thought experiment, imagine if Twitter decided to post fake tweets with any content they want from any Twitter account they wanted to. Is that 'okay'? After all, it's Twitter's platform, they can do whatever they want. I would argue it is not. You could easily construct much worse versions of this thought experiment if this one wasn't sufficient.
Although it's nice that with a free economy one is allowed to create alternative platforms, in practice this has been shown to be much more difficult than in theory, with many attempts being denied service at every level of their operations (banned from their cdn, domain proivder, payment provider, banks, all social media paltforms, etc). A lot of people hate Twitter, Youtube, Facebook, Google, etc, but there are many reasons why these companies are still in complete control.