The place to talk about this is on the massacre talk page but I think you should read the archives to this page very carefully because the problem with the word massacre is exactly the same as with the word WP:TERRORIST a word with intrinsically negative connotations that are generally applied to the actions one's enemies and opponents.

Do you think we should have a page on "Carnage" and "Bloody slaughter" as well as massacre? If not why not?
 
Also I would question much of what you have listed above for example the "Earliest source" which is the area of the OED specalises in is 1578 R. LINDSAY Hist. & Cron. Scotl. (1899) II. 291 The xxiiij day of August..the grytt..murther and messecar of Paris wes committit. for the noun and 1588 J. PENRY Viewe Publ. Wants Wales 65 Men which make no conscience for gaine sake, to breake the law of the æternall, and massaker soules..are dangerous subjects. for the verb and this is a dictionary issue not an encyclopaedia issue. I would go through others but lets skip strait to the categories you have suggested. For example there is a strong case for saying that many massacres are not "Human rights abuses" because the term is attached to many events that are not, or were not human rights abuses. For example there is nothing in the dictionary definition that stops any mass killing within the laws of war being described as a massacre but that is not a human rights abuse, or are you going to make up a roll you own definition?