That's precisely because nobody was talking about any specific country that I've said what I’ve said. A stupid and wrong generalization was being made...

I have no problem believing that in some less democratic countries, it is legally permissible for a private entity to exercise censorship over citizens in general, or over the users of their services. However, fortunately, there are countries where such censorship is illegal, and one of them is Portugal.

In Portugal, if a private entity censors a citizen, the citizen has the right to:
A) Get the removed speech or message reinstated;
B) To be compensated for property and non-pecuniary damages resulting from the censorship;
C) Obtain a compulsory pecuniary penalty for each day of delay in fulfilling the obligation to restore the censored message or speech.

The above legal regime is the result of various legal provisions, mainly enshrined in the Constitution of the Portuguese Republic, the Civil Code and the Code of Civil Procedure. I'm not going to give a detailed analysis of all the legal precepts involved here, not least because some are procedural in nature, and neither is this a law lesson nor am I being paid to give one.

I will say, however, and in direct response to your question, this: the aforementioned regime is constitutionally established in Articles 18 and 37 of the Portuguese Constitution.