what happens when they get a platform?

It may seem contrary, but that's even better! If they get a platform it simply makes them easier to identify and deal with. In fact it opens them up to observation to magnitudes more scrutiny by an ever increasingly aware population.

Then what? De-platform them very publicly in front of this large audience and consider them defeated? No! Let them have their platform. Let them be heard. Let the overwhelming majority of the population that will not tolerate their mindset to condemn them and their behavior. Openly. Over and over and over again until they and some their kind still openly speak, but are no-longer 'heard'.

Let me ask you something. Have you heard anything about Westboro Baptist Church anytime recently, or even in the past several years, or ten? Neither have I. They were allowed to have a voice, display what overwhelming majority considered to be offensive views. They were allowed to do this over and over and over again. They were largely condemned over and over again without silencing their voice. No one talks about them anymore. Not because they were forcibly silenced but because they were not worth anyone's time, and more importantly, the views they held were not agreeable to but a miniscule fraction of the population that people feared before they proved it. Themselves proved they were insignificant.

Give everyone a voice. Willingly. And, I mean EVERYONE. No matter how difficult it seems. This is the only way we fix things.