I'll generally argue with someone I disagree with online, and see if they'll listen to reason. Maybe they'll change their mind, or present new information or a perspective I haven't considered and I'll gain understanding and change my mind.
I only block people who are incapable of arguing in good faith.
After all, what's the point of civic discourse if we're all only talking to people we agree with? It's just preaching to the choir, and creates epistemic bubbles.