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?

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 ...

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.

Does coffee boost longevity? New study may have findings for people in midlife - San Francisco Chronicle

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.

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.

Does red light therapy do anything inside the body, other than just the skin that receives the light? Are there any obscure health benefits?

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.