Keenser, despite being a senior officer, believe it or not (according to the comics he's a lieutenant and is apparently the assistant chief engineer I assume since Kirk does not promote the assistant to be chief), he tkes a lot of abuse and is treated like s skivvy by Scotty in what seems to be a terrible case of workplace bullying and 'disability' discrimination. Plus Scotty does have a history of behaving unprofessionally and abusing animals. He was good in the movie but give more credit to those that really deserve it!
I don't see that at all. I see Keenser and Scotty as having a friendly relationship that is just punctuated by good natured insults, nothing more than that. Scotty is not abusing Keenser, he's just 'needling' the guy. Real friends do that all the time.
And when has Scotty (any version) ever shown any tendency towards "behaving unprofessionally and abusing animals"? Scotty is about the least likely to act that way out of any TOS character.