That is probably the only time something is morally defensible, even if still technically illegal.
BUT - that is rarely actually true. Most people use that as the argument when they can't buy what they want at the PRICE or in the MANNER they want to buy it.
As an example, if a song was not available on iTunes, people would feel ok ripping it from somewhere. But they could have gone out and bought the CD, even used, from Amazon or wherever and then loaded it into their library. The argument would go - "I just want the song - I don't want to have to pay $10 for the whole album to get the song so I'm justified in stealing the song because I can't buy it anywhere." That is b******* - you can buy it, you just can't buy it a la carte. Just like you can't go into a Costco and buy 1 can of soda at Costco level pricing. You can buy one at the convenience store, but it is going to cost you $2.