When people give governments the power to censor information it doesn't take long before that power is misused. What the government has done with this knee-jerk reaction is self-fulfill the prophecy. The government and media have isolated an entire community of nationalists (not just the extremists) which in their minds rationalizes their feelings of oppression. While the government i'm sure had good intentions, how many white nationalists are now out there with a copy of the manifesto and now with festering extremism?
What people don't understand is not all nationalism is white supremacy, and not all nationalism is racism. Just as not all Muslims are terrorists or racists.
And to be fair, this is coming from someone who is quite liberal.