One of the fears atm is that certain companies have more wealth than nation states which means they can effectively dictate rules outside the law.
The issue with censorship is therefore in many respects the same for private companies as it is in terms of it in being in state hands if there is no way to hold that power to account.
The biggest issue with 'twitter law' as it stands is the arbitrary nation of it. Trump had a different set of standards applied to him than others. There is a complete lack of consistency.
There is no transparency over how decisions are made. There is no proper right of reply or a fair appeals system.
The law in the uk is often not being applied - we are subject to the laws as they are in the US and even then thats not necessarily being applied correctly.
There have been concerns that the staff doing this are not well protected from the harms they are trying to stop (PTSD is problematic), there is the ability for staff to act maliciously if they want to users with views they dislike or apply their own ideological views rather than properly censor where they should (examples of clear racism, violence or antisemitism allowed to stand beyond all reasonable justification).
Trump was banned after years of behaviour which by twitters own admission broke their rules. And other leaders who have dubious conduct on the platform have been allowed to stay because?? Because they come from countries that twitter dont really have any interest in terms of their politics.
It gives twitter the power not just to censor but to interfere internationally in politics elsewhere or to enable terrorism / violence elsewhere.
Thats worse than a nation state even an imperialist one in many respect because of its sheer reach.
Theres a huge argument here about what freedom of speech and national / International security meet....
In the uk, we have the principle of free speech however there are limits to this where it involves harm to others in some form (physical, mental and in terms of damage to reputation) or security threats.
The US is different. But there are certainly questions from an European point of view about this and why us freedom of speech offers a clear and present danger to the rest of the world in various ways.