The article said that this guy will from now on keep his dog on a leash and away from the water. This is what he should have done in the first place when he knew that he was on the alligator´s turf. In addition he didn´t have the skill to kill the animal with his knife. Thus he created a hazard for others who have to deal with the animal now and presumeably some pain for the animal. So the alligator has to die because of someone´s lack of common sense (don´t ge me started on the people who still let their children play in the water there). I definitely think that this is no reason to carry a knife. Using common sense would be far better.
I think that carrying a knife is sensible though.