Well then, Data should know that, so if his actions were justified on those grounds there's no reason to lie about it?- The Jovis is a privately owned vessel and thus is outside Starfleet jurisdiction.
For example in"Clues" there was a serious issue with Data not being truthful. And with having a perfect memory there shouldn't be any ambiguity in his recollection of actions or events. Either he fired or he didn't. IMO it's something that should have been handled better in the episode.