Oh, how to tiptoe around this... let's see if I can.
There is really no doubt that Mort was used by sources. Those sources are his employer's most important, and lucrative, business partners. The majority of consumers for both products (the NFL & ESPN) do not care about the truth - they long ago decided what was "true" and what was not, and have no interest in learning more (or that they are, in fact, wrong). The (minority) constituency that does care about the truth (ha!) has engaged in some rather vile behavior in making their dissatisfaction with Mort, his employer, and their business partner known.
Complicating things, a retraction was issued. It was weak, and it was done on Friday night at midnight by someone other than Mort - but it happened. As for why he didn't - well, I think that goes directly to how he was personally treated by DFG Truthers, and by some nominal "peers" like Scott Zolak. I don't think he's "right", but I can see why Mort has decided that his personal suffering at the hands of DFG Truthers has negated the need for him to apologize / own his mistake. And because it is just a "wronged" minority that thinks he should correct the record - and neither his employer, nor their business partner wants him to - he won't. Therefore, it's ok IMO to think Mort is a piece of shit. But in no place else does he have a credibility or integrity problem. He's still seen as a "journalist" in Bristol, in the NFL League Office, and in most NFL markets. In fact, he's probably gonna end up in Canton at some point - which will really make some people mad.
He has no obligation to "out" his sources - and no motivation to do so. The only people who really care are, unfortunately, tied to the DFG Truthers who long ago lost credibility with ... well, everyone. That's just a (sad) fact at this point. Mort "coming clean" would be bad for ESPN and the NFL. That's why it'll never happen. That's why they'll continue to trumpet him, and his "journalistic integrity". If you must, you can chalk up another "victory" for the NFL - they've "won" on brain damage, and they've "won" on domestic abuse, and they "won" on this.