In essence that is what the research is saying - keep using even a plain, vanilla profile shot of an AR-15 and you will generate the association with aggressive behavior.
The media understands its medium. The images are not coincidental or casual. They are purposive and intentional. And moreover, likely to be effective with the non-overlapping hunter class of firearms owners (those who don't also own for self-protection).
You may have noticed of late that many of the manufacturers have been trying to break this association by reframing AR-15 platforms as "modern sporting rifles" and getting away from dark/black finishes. I even think they were making some headway with the purist hunters until Newtown snatched them back.
"I'm your huckleberry."