Actually, white nationalists and other racist groups depend on liberals like you allowing them a platform to appear like a legitimate alternative in the political system. They use that legitimacy to attract new members, and there's a bright line from that to violence to Kristallnacht.
Europeans understand this, which is why they've outlawed Nazism. It's to express as a society that such a thing is not acceptable.
By expressing that it is acceptable, you are participating tacitly.
In contrast, expressing at every point, in every interaction, that white supremacy in all its forms (radical white supremacy, institutionalized white supremacy, cultural appropriation, colonialism, imperialism) is fucked up and fucking wrong and disgusting, you are chipping away at the fascists' resolve. People have a tendency to conform; it is physically difficult not to. In experimental settings, people who have to act nonconformingly feel physically uncomfortable and experience a fight-or-flight response. After experiencing this enough, people will stop being fascists.
In contrast, it's been demonstrated time and again that "rational" argument does nothing but solidify people's pre-existing ideas. So if you want to increase the chance a Nazi stays a Nazi, continue to debate with them. But remember that unlike your high school debate club, the Nazi will, empowered by his strengthened beliefs, go out and kill people. And their blood will be on your hands, because you had a chance to weaken his beliefs instead of making them stronger and you made them stronger.
I think humans maintain their integrity by rejecting all forms of oppression, from patriarchy to white supremacy to homophobia to capitalism, and I think that you sell your integrity away by capitalizing on your privilege and oppressing people, either actively and directly, by being a nazi; actively and indirectly, by arguing for a liberal concept of free speech; passively and directly, by ignoring opportunities to fight when you could; or passively and indirectly, by remaining silent and therefore complicit.
You are wrong, empirically, on every claim you have made, and you are wrong morally, because you have been given a chance to eliminate injustice and have chosen to back the side of oppression.
History is a tidal wave; you can either ride it or be crushed by it. The choice is yours.