It's a tough call, but believe me, being in the air with damage you can't even see is no fun at all!! I don't recommend it!!

It's possible they somehow deduced it would still fly OK, but my guess is it was almost instinctive. They got lucky.
That's a wing designed to hold over 80/90 tonnes of aeroplane in all sort of weather and turbulence with a factor of redundency, and I doubt the tip scrape would have resulted in any more than initial light damage - certainly nothing that would compromise another approach (although diverting to a non crooswind runway could be prudent if worried about control suface damage)
It's possible they could have stopped it safely: they were all the way on the downwind side of the runway and had enough control to take off again, so they might have steered it towards the far upwind corner and laid on the brakes and reverse thrust... might have resulted in lots of damage, but the sight of them lifting off after scraping that wing was almost too much for me! :o
They were struggling with directional control anyway, and by the time they'd got it stable enough to apply brake and use nosewheel steering it may have gone off the other side, or back off to that side.
Tricky, but I
suspect they just about made the right call.