Alternatively by not amplifying their voices Twitter is not morally culpable in supporting them. That is a fair position to take. Additionally, it is a clear signal that the speech "type" has social repercussions in terms of loss of privilege.
I generally agree that by driving them underground, you lose the ability to challenge them, but that has to be weighed against the degree to which they are permitted to spread their ideas by being allowed to spew their rhetoric with impunity.
I don't know that being kicked off twitter will necessarily mean that they grow - but - it will mean that twitter no longer holds a moral responsibility for enabling them.
But this isn't true. Sure, in many cases it is, but once we enter the realm of hate speech and ideologies that pose a threat to the survival of people, good speech is no longer sufficient if you're still allowing the bad speech to continue. If a white supremacist is spouting off their nonsense, you cannot counter that with "good speech", because the people who buy into that ideology aren't going to be swayed by anything you can say. But allowing them to continue espousing their ideology threatens people of other races, because this creates an atmosphere where people think that kind of speech is acceptable, which leads to other worse problems.
The counter argument is that there is 'hate speech' on twitter directed at many types of people and many ideologies that 'threaten the survival of people'. But twitter is only removing certain groups and ideology while sanctioning others that are just as hateful and threatening.
So twitter loses the moral argument that they are trying to prevent these activities. They expose an ideological bias. And by hosting only certain types of 'hate speech' and radical ideologies they are promoting it.
Some countries do have laws against hate speech https://en.wikipedia.org/wiki/Volksverhetzung https://en.wikipedia.org/wiki/Hate_speech_laws_in_Canada
I generally agree that by driving them underground, you lose the ability to challenge them, but that has to be weighed against the degree to which they are permitted to spread their ideas by being allowed to spew their rhetoric with impunity.
I don't know that being kicked off twitter will necessarily mean that they grow - but - it will mean that twitter no longer holds a moral responsibility for enabling them.
I think that's a fair choice to make.