Do not tell. Do not shout. People will not change their opinion if you just tell them they are wrong. Metaphorical shouting, cancelling, no platforming, they do not work. You have to explain patiently, with understanding, with sympathy for why they think what they think. You must understand their assumptions. You must understand your own. You must allow them chance to digest, to ruminate, for that is how one changes an opinion - in anguish, with reluctance, first slowly, privately, long before publicly. You may need to have the discussion twice (or more!), they may need to hear it said from multiple angles and multiple sources.
If you manage some subset of the above then you may play a role (a small one) in changing someone's mind.
But ultimately, you must understand that they may not change their mind. That you might differer in some kind of basic assumption which would mean that they would never, could never, agree with your argument.
If you do it right, there is the possibility that they may change yours.
But perhaps the worst outcome, indeed possibly the most correct, might be that they leave you riddled with doubt.