That is true. You can't debate everyone on an even playing field, because not everyone has the same baseline views of morality and reason.

More and more, I have come to think that debates are better for convincing undecided bystanders than convincing the other person you're debating with. At least for arguments or debates held online or in a public space.

One-on-one you might be able to show someone a new value system if they're willing to sit down and talk about it, though.