Of course, let's also not forget that there is a culture that has made a point of shouting down contrarian or critical viewpoints when a discussion could be initiated.
Worried that perhaps some vaccinations are unnecessary? You're a stupid anti-vaxxer.
Critical of environmental science methodology? You're a climate change denier (and probably in the pocket of Big Oil).
Not a fan of how Black Lives Matter conducts some of their protests, or perhaps you think that using ID to combat potential voter fraud is a valid idea? You're a racist.
Not a supporter of a specific presidential candidate? Well, it's probably because you're a misogynist...and there's a good chance you're rather deplorable as well.
That's a good part of why people have stayed silent: they're demonized before a conversation can begin. It's not necessarily because they didn't want to have a conversation.
If you're being shouted down, regardless of why one party thinks you should be shouted down, your worldview and opinion of the opposite party will be strongly affected.