I took out a new Credit card which had a 0% for 32 months offer. I then took the largest balance transfer I could, (£15000) and used it to pay off a chunk of mortgage at 3.54%
I don't see this as any different. If you have debt, then you're better off having it at the lowest interest rate possible.
He might have just spent 30k on strippers and coke, in which case his decisions suck, but equally, it could be 30k on doing up a house he is about to flip, and low interest credit is the best way of financing the deal.
Making assumptions on why he needs 30k of credit doesn't change the fact that having that much at such low interest in a fantastic deal,