Some individuals are more interested in playing up to the "feel good" crowd, and want to pad their stats in any way possible, without having to do much work. This is why they'll go after the easy targets that they know won't cause any fracass to them. They're going after the wrong people, of course, but they'll do anything to make themselves look good, while avoiding the real problem in a cowardly manner.
While this example was in the UK, things like this do happen in the US as well. For example, if we look at the "zero tolerance" policies that were enacted in various schools, we can see a multitude of instances that can only make us raise an eyebrow, wondering what the heck is going on.
One such example is a "zero tolerance on drugs" policy, where students who are caught with a single Advil or Aleve tablet, are put through a witch hunt, suspended, or even expelled, for violating the drug policies. At the same time, the real drug pushers, such as the gangbangers, are left alone, since a politically correct school system doesn't want to "target" minorities. Either that, or (more precisely) they lack the intestinal fortitude to do the right thing. Still, the school board can then say "Oh yeah, we busted yet another violator of the drug-free policy!"
The same thing applies to the weapons policies, where children have been kicked out of school for having those tiny plastic sword toothpicks that hold sandwiches together, or when a parent had packed a plastic knife in the lunch box so that the child could spread peanut butter on bread. At the same time, gangbangers who have ice picks, switchblades, and yes, even firearms, are blissfully ignored.
The civilized world needs to wake up and smell the coffee. Stop targeting the wrong people, and go after the truly bad elements of society instead.