Why isn't the FBI raiding all Silicon Valley companies like Facebook, Twitter, Instagram, WhatsApp, TikTok, Reddit, Google, Yahoo, YouTube, Disqus, Wikipedia for censoring the World through their Ban cartel violating the constitution freespeech laws?

Lemme make this simple - Freedom of the press belongs to the person who owns the press. You don’t like what a particular press (the social media you reference above is the press in this case) does, start your own and you make the rules.

Government owned companies are also covered by this, but these companies must allow speech the company may not agree with.

Restrictions of course apply. See Supreme Court rulings on what can be restricted, i.e. child porn, inciting to violence and a couple of others.

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They have not violated the U.S. Constitution and freedom of speech laws. Dunno about other countries.

Should newspapers be forced to print every letter ...

What arguments like this fail to recognize is 1A means you have the right to keep your damfool mouth shut. 1A means you cannot be forced to say anything, a right backed up by 5A. 1A and 5A as they apply to speech prevent government from forcing you to say something AND stop government from not letting you speak.

Canadians went out of their way to help Americans stranded in Canada after 9.11.2001. Why did Canadians help so much the way they did? We read that Canadians don't particularly like Americans to begin with.

Companies that are privately owned, owned by stockholders, etc. are also covered by this. These companies cannot be forced to provide space or a platform for speech they do not agree with. This is freedom of speech. I realize you may disagree.