White nationalists are evil simply because of the inferiority and superiority belief which are extreme forms of one's culture. That being said, such extremes are the result of various documented murders as well as potentially undocumented murders. Slavery and the creation of systemic racism is a clear form of white nationalism and supremacy.
White supremacists/nationalists are our biggest threat and unfortunately the media does not recognize that because it is easier to paint the boogie man brown or black as opposed to white (see:
White supremacists committed most extremist killings in 2017, ADL says).
In the case of cruz he was an indoctrinated white nationalist imp and anytime the FBI is doing an investigation sure, a group is going to disavow their association because they too will be investigated and their operation whether covert or not, will to be investigated. The leader in this case was just that dumb and had to recall his answer. But it is well documented that Nikolas Cruz was a racist and held racist views:
"On social media, Nikolas Cruz did not appear to be a peaceful man. He made quite clear his desire to perpetrate the exact type of violence of which he now stands accused.
Before he allegedly committed one of the worst mass shootings in US history at a Parkland, Florida, high school on Wednesday, police officials say Cruz wrote social media posts so threatening he was reported to the FBI.
He hurled slurs at blacks and Muslims, and according to the Anti-Defamation League, had ties to white supremacists. He said he would shoot people with his AR-15 and singled out police and anti-fascist protesters as deserving of his vengeance."
See:
Nikolas Cruz's digital profile 'very, very disturbing' - CNN
You do realize there are Jews who are also ethnically European/White and even they are targeted due to not having pure "aryan blood" so that fails. Part of the philosophy of white nationalism is about the purity of one's genetic line. If you aren't pure white you're considered a "mixed breed" and discarded from the fold. White supremacists have been targeting other whites for decades simply for associating with people of color this is why you will get terms like "n***er lover" thrown around since my grand father's time.
The point is if you hold ethnic views of supremacy in a multi-cultural setting it becomes more dangerous because your beliefs in their extreme form may supersede rational judgment. You cannot be a white nationalist and teach political science and even if you do, you better be damn good at lying and holding in your own personal judgment. People with this mindset is dangerous and qualified or not, should not be having no concealed weapons around kids of different ethnic backgrounds.