Selective enforcement of private contracts is totally legal, and the EU('s executive branch) is uncomfortable with the public policy implications of that when it comes to social media and would like new laws passed to add extra regulation on uniformity and specificity of moderation policies.
I think that some cases whereby $importantperson isn't banned because they're important are valid. It helps to have a public and verifiable record of a public office holder making provably false claims, particularly when a warning is then slathered over said bullshit. But the thought of a government body deciding when a company may and may not enforce its rules is chilling.
In general I agree with you; I only consider this kind of thinking valid at Twitter/FB/Google/AWS scale - where one decision affects populations the size of entire nations (or larger). It's a problem less than a dozen companies would ever face and any reasonable law would need to make that abundantly clear. I wouldn't favor opening that door for smaller companies.