The ACLU seems like a worthwhile cause for actual advocates of free speech. And no, they don't only advocate for liberal causes. Campaign finance laws would be one area of policy where they have starkly different ideas than the political left.
As to these platforms: the whole argument is essentially build on this slippery-slope fallacy that banning vile racism, anti-semitism, etc. inexorably leads more restrictions on speech, and (eventually) the end democracy.
That's demonstrably false: there have always been restrictions on speech (such as obscenity laws), so there really isn't some bright red line that would be crossed, and these restrictions have also not lead to the end of free speech.
There are restrictions on almost any other activity if you expand your definitions to the extremes: the right of peaceful assembly is just as central to democracy, but nobody is bothered by the restriction that you can't hold your protest in the Oval Office.
So maybe these people should consider being kicked out of all these platforms not as an incentive to change platforms, but to rather think about how far they must have removed themselves from society. Seriously: if the people who think youtube comments are worth it ban you, it's time to start listening more and posting less.