Think of the last hundred years, the countries that supported some form of free expression and discourse are now the most progressive rational societies on the planet. And the ones that enforced moral standards and 'ministries of truth', usually religious, are the most regressive.

It doesn't matter whether you can change someones mind on the spot, it matters that your argument is superior and the public tend to repeat and re-argue the superior argument. And yes, things like election fraud, that might be possible, and has happened before, is harder to argued against than a flat earth. But these positions are also the ones where we might be wrong.