I don't believe being against hate is a "leftist" worldview; it's a widely accepted and healthy one. In a way, you agree:
> their politics are the ones supported by "The System" and that they are perhaps not the rebels they thought they were?
Certainly there is a very well-established and long history, and continuing practice, of prejudice in government against (almost any group besides white Christian males, as a shorthand for a long list). There is also now a countervailing force, protecting the freedoms and asserting the interests of the oppressed groups. The existence of both forces can't seriously be questioned.
But going back to my first sentence: Really, that's the fundamental debate going on in this HN thread and in many others: Some assert, implicitly, that the hate groups are just another point of view, and that they are inherently no better or worse than other POVs. Others, including Google, disagree.
Sometimes that argument is made using extreme relativism or political correctness: All POVs have the same merit and deserve equal treatment; it's politically incorrect to discriminate at all. While that's an interesting and valuable philosophical discussion - how do we distinguish perfectly between good and bad - we can and must still distinguish between them. We don't have to wait for the perfect philosophical solution.
But we can approach the question with reason: First, I believe that many (not all) arguing that the hate groups should be heard simply support the hate groups - it has nothing to do with public interest or freedom of speech; probably that's true on the other side too. Second, a more reasoned argument: Why should we tolerate groups who don't tolerate others? It breaks a fudamental social contract of free societies: If you want me to respect you, you must respect me.