Did he pick up the time as allowed by the current contract? If so, then you have NOTHING to complain about.

Now if he did it outside the contract by making deals with the crew scheduler, then that becomes an issue.

Everyone should use the contract to their individual benefit. If one pilot likes to drop down to minimums to extend his days off is that a problem? Why then if another sells his vacation back and flies a full month is that a problem?

Fly the contract. Maximize it to YOUR PERSONAL benefit. There's nothing wrong with that.