Probably not.
Speaking as a debtor, there's really two issues in dealing with creditors: a moral issue and a legal issue. From the creditor's point of view there's also a business issue, and probably no moral issue at all. The stockholders are interested in pennies per share earned during the quarter, and couldn't care less whether the debtors are good, bad, or indifferent.
I've already discussed the business aspect.
The moral issue is pretty vague, from my point of view, by the time the debt is sold off. The original creditor has been paid what he regards as a fair price. The purchaser bought a risk of nonpayment, on the assumption that there'll be enough payment in the lot to make it worthwhile. To me, the moral issue relates to one's duty to honor his obligation to his legitimate creditor, but if the old creditor doesn't care anymore, and the new creditor really doesn't care that much, I'm not sure I do either. Especially if they don't bother to get the information they need to be able to collect and keep it straight.
See, when they send a demand letter that says, "Joe Bloe, you owe X dollars, the original creditor is Flurg Corporation, account number 007", and Joe really did have a debt with Flurg, account number 007, but the amount wasn't X, it was Y, then the statement is a false statement, and Joe can legitimately deny the debt. Now most folks really don't have the accounting background (myself included) to really understand stuff like compound interest and interest on fees and late fees on top of late fees and prepayment penalties. So it's entirely possible that Joe really does owe X, he's mistaken thinking he owes Y. It's still appropriate to deny the debt and demand verification under the fdcpa - if they can provide the verification, explanation as to why they think he owes X in sufficient detail that a judge looking at it later would say it makes sense, then he can recognize that he's mistaken and pay up or make arrangements to pay up. But if they don't have the paperwork to show that he really does owe X such that they can set him straight by a proper response to the demand for verification, then he can legitimately say he doesn't owe that debt at all. Maybe he once owed a different debt that he's never paid, but if Flurg wrote it off or discounted it, then it's gone as far as Flurg is concerned. If Flurg didn't bother to send Joe notice that he's supposed to pay someone else, then Joe can legitimately claim he owes Y to Flurg and to no one else.
So, as a legal matter, I'd say Joe doesn't owe X to Newcreditor Collections, Inc. And if they can't prove he does by responding to a demand for verification, he's entirely justified in taking that position. And if Newcreditor Collections reports it to a credit bureau without having responded to a demand for verification, I'd say that was both libel and a violation of the Fair Credit Reporting Act.
Similarly, if the statute of limitations has expired, as a legal matter there's still a debt, but it's legally uncollectable. That's because statute of limitations is an affirmative defense that has to be stated in writing in pleadings when one is sued on the debt. It's a "use it or lose it" kind of thing. So a stale debt can still be reported but the debtor could get a letter stuck in the credit bureau's file that says, "I once had a debt to Flurg for Y, but they never acted to collect it. Newcreditor Collections says I owe them X, but that's not true. And the statute of limitations has expired, so I don't owe anybody anything." As a moral issue, that I assert businesses generally don't care about, he could also say, "I was willing to pay Flurg the Y I owed them, but they didn't want it. I'm still willing to do so notwithstanding the statute of limitations, if only they'd send me a corrected bill." (I wouldn't do anything like that, myself, because the stuff can't stay in the credit file all that long, measured from the time of the default, and anyone looking at the file will see it was a stale debt they didn't bother to sue on - besides I wouldn't make a waiver of my rights that way, 'cause you can lose them if you say stuff like that).
My feeling is that the System (or the Beast as some fans of the Book of Revelation put it) is a nonmoral thing. To participate in the System, one has to adopt the System's assumptions. So I treat dealing with the System only from a business and legal standpoint. When I'm dealing with creditors, on behalf of a client, I'm ethically obligated to pursue my client's best interests with respect to that creditor without any regard for whether I personally feel the client "should" or "ought to" pay the creditor. I don't get involved until the spaghetti has already hit the fan, generally, and at that point, it's all legal strategy and wrangling.
I think that the moral aspect is best explained in the Book of Proverbs, that I'd sum up thus: live with self-discipline, not self-indulgence; pay as you go, live within your means; tithe a bit, save a bit, and spend the rest with joy, peace, and thanksgiving. Once that spaghetti is in the fan, it's too late to worry about all that stuff. Best thing at that point is to try to figure out how to be getting better.