So much of what we see today regarding opinions on politics and history are simply conformity to "the group." Civil War historiography is a perfect example. It was about slavery. Divert from that "groupthink" opinion and you're a "Lost-Causer" or a "neo-Confederate." The establishment attempts to shame you into submission. This is nothing new, of course. Mark Twain wrote about it in his day:
If he would prosper, he must train with the majority; in matters of large moment, like politics and religion, he must think and feel with the bulk of his neighbors, or suffer damage in his social standing and in his business prosperities. He must restrict himself to corn-pone opinions – at least on the surface. He must get his opinions from other people; he must reason out none for himself; he must have no first-hand views.
"If he would prosper" - yes, I recall a pseudo-historian who once stated he was getting "better gigs" since he started "training with the majority."
And . . .
We know it is a matter of association and sympathy, not reasoning and examination; that hardly a man in the world has an opinion upon morals, politics, or religion which he got otherwise than through his associations and sympathies. Broadly speaking, there are none but corn-pone opinions. And broadly speaking, corn-pone stands for self-approval. Self-approval is acquired mainly from the approval of other people. The result is conformity. Sometimes conformity has a sordid business interest – the bread-and-butter interest – but not in most cases, I think. I think that in the majority of cases it is unconscious and not calculated; that it is born of the human being's natural yearning to stand well with his fellows and have their inspiring approval and praise – a yearning which is commonly so strong and so insistent that it cannot be effectually resisted, and must have its way.
More of Twain's wisdom on this topic here.