Free speech is a powerful thing, which means it can be used for good and for bad. Sometimes what appears to us today as bad can actually turn out to be good in the future.
The general rule of free speech is that it does not permit threats of violence or obvious incitement to violence.
Hate speech, on the other hand, is MUCH more subjective. What may appear to me to be a well-reasoned argument may to you appear to be hate speech.
With these complex issues in mind, I'd say that unless the groups that Reddit banned were advocating or threatening violence, banning them was counter-productive and hurtful to having an open and free discourse on the internet.
Of course, there is the go-to argument that Reddit is a private company, and as such they can do whatever they like, but because they provide a public service that is used by billions of people, they have an obligation to uphold the values and laws of our society - most notably the first amendment - which protects free speech.