It's an emotional time, and people are seeking to explain the seemingly inexplicable, with words such as evil. The individual that called into the show appeared to be taking the "straw that broke the camel's back" approach, while Nick seemed to be very much pointing to individual responsibility, alongside the right to be offended.
I happen to agree with Nick's stance on this, but in a qualified way. We can no further understand the motivations of any other individual than we can at times understand our own. Nick assumed that Omar was seeking to justify the actions of those involved, which may well have been his intent, but also may not have been.
I've not heard the entire show, so I'm not going to comment either way on that score. I do believe however that in seeking individual responsibility we must also seek understanding. No matter how unjustified the motivation for these killings was, if we don't seek to understand them at some level, we cannot prevent recurrences.
For me the tendency to use the word evil is dangerous, as is the tendency to assign blame. Blame is the lazy way to deal with crime, punishment, and security in general. It is a process that justifies prison as a punishment, yet ignores the importance of rehabilitation, as well as prevention. It sees poverty as a personal circumstance rather than a societal failure, for example.
So, whilst I agree with Nick about the right to offend, and about the fact that murder is never justified, I don't see any point in blame. If anything I see the need for a potentially much colder, and even darker, analysis. Now is a time to ask, what is society willing to do to ensure this type of act becomes completely unpalatable, no matter the potential reasoning behind it?
Such an approach to thinking about this can go two ways though. One is authoritarian, surveillance based and involves the restriction of freedom to the point that fear serves to prevent a recurrence. Another route, perhaps harder on those with the most to lose, is to put some serious effort into reforming humanity as a whole, to the point that our very humanity prevents recurrence.
I personally hope for the latter, but I am sure plenty will be happy with the former.