I basically agree with you. As for "but cannot attend this protest if it will be all about Bill Gates, anti-vaxxers, Trump, Brexit, far-fetched plandemic theories, etc" I would just ask where on the flyer it suggests that the event will be about any of those topics? That's likely the angle the media will take if they choose to report on it, but everyone is welcome to attend and air their own personal views, that's kind of the point really.

"I would join a protest if it was about basic principles of liberty, human rights and democracy; government has no right to lock us in our homes, mandate us to wear face coverings, shut down our businesses, distort markets and wreck the economy in the process"
You are essentially describing the entire premise for the protest.