These folks aren't doing this because they've immersed themselves in Islam's intellectual and social potential as a doctrine and a faith.
These are largely yobbos with the basics. Who clutch the basics all the more tightly because they don't have the inclination or wit to get beyond them.
And ideology is probably too unitary a term. Islam is pretty diffuse.
I know it's diffuse, but the issue is this sort of grouping. They are yobbos under a particular ideology, not mainstream but still evidently not small in number.
As soon as you call for death, you lose respect in a civilised society. No doubt there will be imams who decry this event, but the ones who apologise aren't the ones at fault. The people who are to blame will remain anonymous and fan the flames when it suits them. These are the bad apples.