I did that once, afterwards they hated me.

Face to face, this is definitely possible. I've convinced more than a dozen people that climate change is real, and humans are the primary cause of it in face to face conversation. Online, where tone is easily misinterpreted, everyone is a stranger, and people are more able to rapidly retreat into a bubble of others that agree with them, I think it does a lot less good - but every once in a while, something works a little bit for someone.

More importantly, if we decide that we should all exist in our isolated bubbles of (non)social acceptance, it leads to the rise of extremism in some of those groups, and even the most terrible ideas can be allowed to fester and grow. Pretty much regardless of who you are, or what you believe, you probably have an example or two of such beliefs.