Online is the wrong place. Try in person. And keep going. Just have normal conversations. Don't explicitly try to convince anyone of anything. Just ask questions, have a laugh, get people to think. Over four years, one of those conversations will bear fruit.
Here’s the thing…I’m a lawyer, I’m trained to ask questions & choose my words carefully - in respect of any dialogue with leave voters, there isn’t any fucking English language that encourages more than them putting their fingers in their ears. You seem uniquely capable.