Edit: I think you're right about reaching out, btw.
"Those pesky proles wouldn't actually vote Leave, and even if a few do there's no way it will be a majority, so we can stay the course with the EU because that's all we are offering and they are gonna have to take it either way." - my mental image of center-left politicians.
Exact same attitude annointed Clinton with the nomination.
Liberals already tried that this election, it's still impossible to go a day without a MSM outlet saying Trump is literally Hitler and that America is now a fascist state. It's probably not wise to eschew diplomacy when the GOP is as powerful at all levels of government from local to national as they have been in 80 years.
I think your definition of mainstream media is overly broad.
Yes, as a matter of fact, they did. Trump flipped a lot of counties that went for Obama twice. I recommend you follow his example. Find some people on the other side who should be persuadable, and get to persuadin'.