First, the Leave campaign cheated. They lied, and they peddled foreign influence. Cheaters in sports get stripped of any titles their cheating played a role in. Why shouldn’t cheaters in politics suffer a similar fate, particularly given how the consequences of their cheating can be vastly more severe?
Second, decisions shouldn’t always be irrevocable. We’ve all done things we regret, only to back out as best we can and admit we were wrong for making what hindsight showed to be a wrong decision in the first place. Sure, some decisions are intrinsically hard to undo, but why should that be used as an excuse for making all decisions artificially difficult to undo?
Hold another referendum. If it fails, try as hard as possible to shit-can the whole misadventure. In such a case, it’s likely the rest of the EU will go along with Britain’s wishes; the trade disruption caused by a Brexit would hurt the Continent, too.