Most teenagers have mental maturity issues with the whole "shades of grey" thing...not like the 50 shades of grey book...but that they see things in only black and white, good or evil. There's no real breakdown of understanding as to how people are both good and bad all at the same time.
Basically they are extremely idealistic in nature. Because that's what their cognitive function is limiting them to understand at the time. The more advanced cognitive stuff comes on slowly later.
So when a teenager sees something that is blatantly wrong...like a legal immigrant's (minority owned business) getting destroyed and looted because of something that happened elsewhere and the city government isn't doing enough to stop it...a teenager will rise up and get angry and do something about it.
No, Kyle didn't go to the riot to "mow everyone down"...he wanted to be a beacon of light and hope and kindness for some very angry people while helping minority businessmen save their business.
And then the thugs came along to end his life.
They used the fire as a lure to isolate him...and then attacked. They use similar tactics in prison to isolate guards and attack them as well. But jailhouse guards have training to not get isolated as well as well organized backup plans in place.
And then the weight of the justice system came against Kyle (because of political hacks) and the whole thing became a David vs Goliath story.
The main stream media and even the president were condemning him for surviving what should have been a deadly attack on his life. And because Kyle not only survived but killed some of the worst elements of our society...he found a groundswell of support against a "Grandmother beater", "Girlfriend abuser/rapist" and a pedophile and the impotent government trying to abuse a young man simply trying to do some good.
And now we are asking for his assistance once again by seeking vengeance against those who abused him. The media who lied, the president who maligned, and others who rushed to condemn him because of politics.