Given that its a car on a personal contact plan, I would imagine the car is worth the money that he owes on it, as thats how PCP tends to work assuming you put down a reasonable deposit.
Providing you can afford the monthly payments for the period of the loan, I fail to see how it instantly makes you a twat?

Some of the deals are so good on PCP at the moment (like 0% interest) that its actually worth doing even if you have the money in the bank, especially given that the value of the car at the end of the loan period is guarenteed, so its a KNOWN outgoing, where as if you buy a car outright, you have no idea what it will be worth in 3 years when you have finished with it.

Now personally I would tend to try and avoid finance on anything, as typically it costs money, but I certainly disagree it makes someone a twat to do it, especially without knowing the circumstances, it could very possibly be the absolute best way of him owning that car for all you know!