Opinions, and speech, have power. Otherwise there wouldn't be a point in engaging in it. "Having power" is synonymous with the ability to cause harm. Therefore, some speech is harmful.
When someone spreads opinions that someone else considers dangerous, a deeply human mechanism kicks in: criticising/shaming/isolating.
These aren't new mechanisms. Beginning with the first species that formed groups of cooperation, i.e. societies, there was a need to establish and defend group norms. Today, the harshest mechanisms to correct people who behave in ways that are considered harmful are criminal laws. But long before we get to the level of crime, each one of us uses a repertoire of behaviours meant to inform you of your transgressions, and to put the perceived cost of them on you.
This starts with your father's raised eyebrow when you're interrupting your sister (again!). It's the teacher calling you out for being lazy. And it's the teammates not talking to you after you lost them the match.
These mechanisms escalate along with the perceived harm. It starts with subtle hints that you should work more diligently, and only when such attempts fail, it escalates to direct appeals, or even the loss of your job.
Political opinions aren't somehow exempt from the judgement by others. If there's a real danger that a reasonable employer will fire you for you political opinion, don't ask "who will be targeted next?". Ask just how far from the pack have you strayed?