I suppose people have always insulted their political opponents: "Tory scum" is hardly a new coinage. But it's only recently (in this country, at least) that people seem to have started suggesting that their political opponents are so irresponsible/evil/stupid that they should not be allowed to vote, or that their votes should be ignored.
I won't say it began with Brexit, but it's been very noticeable in its wake. The narrative that those who voted Leave should be overruled because they were a) too racist, b) too stupid, c) have probably changed their minds by now, etc., kicked in pretty much immediately after the vote. Even if all these things were true, though, it doesn't change the result: in a democracy, even stupid people get a say. If you don't like it, then why not just come out and say honestly that you would rather have a different kind of political system - a government of technocrats, for example, like Mario Monti's or Xi Jinping's? A case could be made, I'm sure. What you don't get to do is call the result democratic. Yet, in a wonderful but it seems unconscious irony, one of the movements to overturn the referendum result and take the power to decide on Brexit away from the voters has named itself "the People's Challenge". That kind of double-think is not untypical of political discourse in the UK today.
The result of the last Labour leadership election (and probably the next) is another case in point. The determination of many people not to see Corbyn's victory as legitimate, except in the trifling and legalistic sense that he got more votes than anyone else, is bolstered by a move to delegitimize the views of those who voted (or intend to vote) for him. Here I don't refer to the literal disenfranchisement of 130,000 Labour members by the NEC, though that's not irrelevant, but to the dismissive way in which those who support Corbyn's position are routinely described: they are members of a cult, they are bewitched, they are too young to understand the issues, they have had their arms twisted by Trots, they are Trots, they are "Nazi stormtroopers", or simply (as Financial Times journalist Janan Ganesh has it) "as thick as pigshit". Otherwise, they wouldn't be voting for a "lunatic",* would they? Given that, their views and votes can be safely ignored, and we can start undermining the result the day after it's announced, secure in the knowledge that we are defending democracy, war is peace, freedom is slavery, etc.
* Copyright Owen Smith.