I don't think its just simple ignorance. Nor is it entirely an "evil" agenda. ITs both, in combination.
The guy in the effects dept who is told "get me a clip of a guy shooting for this segment" might not have a personal anti gun agenda. The reporter on screen might not (although those who disagree with the boss seldom get much airtime), but the bosses and the owners who make the high level decisions about general policies DO have an agenda. Some of them have two.
The one agenda shared by all of them is to make money. Today, everything seems to be grist for that mill. Maybe it always was, but once upon a time, it seemed to me that being right (accurate) was more important than being first to report...something.
back in the early 80s, Time magazine printed an editorial that said, basically, that while journalists should be neutral and objective, some issues were too important for them not to take sides. And Time magazine was taking the side against personal ownership of firearms. They actually printed that, once. So, for being honest about taking that position, I respect them. For actually taking that position, I consider them boneheaded idiots, but I do respect them for not pretending to be otherwise in this matter.
As for the tactics they use to press their agenda, and the accuracy of their reporting, I have no respect at all.