As @animats points out, the research is not using accepted Olweus’s definition of bullying.
Instead they use aggression and bind it to bullying.
This very much scares me, specially how Kinney's aggression includes verbal and indirect aggression.
There are clear cases where most can agree something is verbal aggression. My fear is in defining the edges of these verbal exchanges.
Who decides the words said were aggressive?
In essence, the research reads like a further lowering tolerance bar for others' verbal expression.
In a dystopian world, the solution would be where all communications is passed through a system, and pre-approved prior to transmitting it to the other party.
Sort of like some system, say a social (media) service where we only display pleasing and pleasant images and text with appropriate tiny pictures representing positive feelings, while the service provider shelters us from aggressive thoughts.
personal anecdote: I was in the grocery store waiting for sliced cheese. The customer that was at the counter, asked for something and got into a conversation with the clerk while he was slicing, but I could not make out most of it. I heard "blah blah, and you can make blah blah great again!" The man behind me start yelling, how the customer at the counter was a (insert curse words, lots of WWII references), and cheese customer should die right there, we should all lynch cheese customer, and on and on...
The cheese customer's words were verbal aggression to the yelling man. Turns out cheese customer was talking about some engine oil for the clerk's high mileage car.
Was the cheese customer a bully? Was the yelling man behind me a victim of aggression? Was the yelling man bullied by the cheese customer? What if the discussion was between the cheese customer and yelling victim?
I am not trying to be flippant as these incidents no longer are theoretical, "oh this will never happen" scenario. I have seen other similar violent reactions from people just when the "wrong words" or words deemed by the hearer aggressive were uttered.