I can understand the viewpoint you have, though I don't agree with it.
Radical ideas have always looked for ways to spread around and influence people. As in with any idea, there are good ones (Why should a worker not have paid holidays, or days off, or have work life balance, education rights, voting rights, etc) and bad ones (the ones we see espoused by many radical right wingers like the claimed inferiority of the black race and the superiority of the white race)
Now, 74 million Americans voted for a vision of trump, that mixes a lot of good ideas with some very terrible ones. And out of the 74 million voters for him, I am sure many of them voted for the promise of jobs, stability, incomes, etc. Unfortunately, a significant & vocal minority of his supporters have shown hard right and often immoral ideas.
In the past, messaging and reach was a carefully cultivated art practiced by seasoned politicians and ideologists.
Today, the situation is different. It is very very easy to gather people into a group, isolate them and radicalize them. You see it happening everyday on the social media.
What, then, is the solution to this? It is a problem because a society must be coherent and move forward together, otherwise it fractures and implodes from within.
For a society, there are many aspects that affect it's prosperity. Jobs, distribution of wealth, prevalence of opportunities, justice, etc.
If you have allow one small section of ideologues hijack the conversation and demand for continuation of radicalization, that society will collapse. Just think about Nazism, Stalinism, etc. All those societies had one thing in common, the ability to radicalize and brainwash population.
So what about Parler? Banning is the right thing to do.
Out of those 74 million who voted, they have avenues like FB, Twitter, IG, etc to engage and communicate.
That small group who wants to radicalize the society, have their voices cut off, and that is how it should be.