Ah, I wrote that post in jest ! I was poking fun at some of the posters over in the Lore forum who only seem to function when there's complaints to do about the writers with how they're writing certain characters/groups arcs.
I am pointing out merely that this is all a fictional world where none of these characters/groups have motivations of their own accord, it's all at the behest of what the dev team implements.
But I do agree with your post that a schism formed from the foundation of hatred for the opposing faction fits more, and actually I think that
is what Blizzard has been doing after TBC. In MoP the Purge of Dalaran involved the factional allegiances to a greater degree than simply High Elf/Blood Elf hate (though that did still exist). You see it during the Reckoning bit with Taran Zhu as well -> despite there being Blood Elf soldiers vs High Elf soldiers the squabbles brought up are faction-based (Vereesa referencing the death of Rhonin aka Mana bombing Theramore) (Jaina mentioning how 'they' [Horde] have squandered every attempt at peace).
More than likely because at TBC's culmination the Blood Elves are no longer the "mana vampires" they were introduced as.
Even when the Purge is brought up again during the War Campaign, the Sunreavers are aiming their vengeance at the Alliance as a whole and not merely the High Elves nor only Jaina.
Magister Umbric in his commentary makes mention that he and his group never agreed that joining the Horde was good/right and feels the Alliance are where the Thalassians belong.
Vereesa in the Three Sisters comic talks about Blood Elves making the "right choice" (paraphrasing) about coming back to the Alliance and Sylvanas scoffing that they're where they want to be (in the Horde).
So I think we are actually seeing that, and Silver Covenant has always been against the Horde in general, forming up because they refused to accept the Council allowing Sunreavers (Horde Blood Elves) into the city of Dalaran.
But overall I do agree, that's a much better focus of hate (the factions) for the High Elf/Blood Elf schism!