Jets hire Aaron Glenn as Head Coach per Josina Anderson

It's not wrong to tweet that someone familiar with Glenn disagreed with that report if someone familiar with Glenn told Underhill that he disagreed with that report. He was probably being fed something from the Glenn camp to keep the Saints/Saints fans on the hook in case the Jets did not come through with his demands (GM, salary, etc.). But he's not wrong for tweeting that he heard a thing that he heard.
Not wrong per se, I agree. Underhill may want to vet his sources better, or get more confirmation, though, before repeating claims, rather than let himself be used to pass on information that is self-serving to a particular party and is more in the interest of said party than of Saints fans.