Dehumanisation of the Other is the first step to fascism.
Suggesting that people are intellectually or morally inferior to you based on a political choice they've made is the literal thin end of the wedge.
Not to go all "this why Trump/Leave won" but this is why Trump and Leave won.
17.4 million people voted for Brexit and 60 odd million voted for Trump. That should have been a wake up call that it's a mainstream opinion by a near majority of the people that they are not being listened to, their concerns are not being addressed and worse than that when they take the action that our society says is their proper expression of will, they get demonized for it.
I said this right after the Leave vote but this was the signal for the left in the UK to stop talking and start actually listening. To their credit, Labour reformed. I don't personally agree that they've gone in the proper direction with that report but they at least tried to address their failings as a political party and understand what the man or woman on the streets wants in 2018 and what issues they're facing.
What they didn't do is call everybody evil or idiots for voting in a way they didn't want them to. Stunningly, that doesnt make people feel listened to and want to vote for you. Political parties don't exist to be served by the people, they exist to serve the people.
Feeling moral superiority over the colour of the tie that you voted for is incredible arrogance.