> sacred knowledge?

I think you might be romanticizing this, a bit. When you convince the public that not talking about something is the best course of action, they become a lot easier to control. We learned this during WWII with the propaganda machine that was fully employed on all fronts, and arguably before that with the work of Edward Bernays and people like him. If public discourse and debate could be quashed, then it was much, much easier to simply tell everyone what their opinions of a thing should be.

Where do I say not to talk about it?

I think that on its face the term "sacred knowledge" kind of communicates an intimacy that indicates that it's not something that's shared with people who don't have a privileged relationship with you.

I think the big difference now is that people have a megaphone in the form of social media and they forget just how wide the statements they shout through it can spread.

Prior to secret ballots being a thing you would have voted "viva voce" by saying your preference aloud. Violence and intimidation were common.

I think generally people are I'll equipped to engage publicly in politics. Politics is an extremely dirty game and can be extremely divisive.

My friends are willing to give me the benefit of the doubt. Strangers usually only offer shallow ridicule and trolling- especially online.