Though many people do it anyway, the claim to be a Christian believer and LGBTQ is a pretty difficult mental tightrope to walk. Jesus teaching and everything else found in the Bible is all pretty crystal clear on the subject.
So when some people try to do both they often run into someone who has studied the Bible extensively who won't join them in their distortion of what it says. And sometimes that person's resulting anger gets directed at the person being honest when really they are just mad at God.
I've had plenty of youth get pretty mad at me for pointing out the flaws in their biblical contortions over the years. Luckily none as unstable and violent as this radicalized young person obviously became.