Data could tell Odo about the time he attempted to kill Kivas Fajo, and Odo could offer his input as to the moral and law enforcement ramifications of Data's actions and attempted actions.
Data: "What would you have done?"
Odo: "That's a good question."
Well Odo was in a similar situation when Tain and Garak captured him. We'll never know for sure given Garak had his anti-shape shifter machine, but I was under the distinct impression Odo was about to give him a beating.
Mind you it would probably be just to the point of unconsciousness, and Odo did save Garak's life despite it all. Really though, Odo had a demonstrated behavior of putting his own sense of justice before letter of the law and morality.
He had no problem working as the literal equivalent of a Gestapo agent during the occupation. In fact he often pines on how those were the good old days when everything was kept secure. He often chafes at Federation due process, he'll lock Quark up without charges our representation regularly, he wanted to break up Rom's union because he thought they were bad for public order, and he offered to arrest a bunch of Paigh wraith cultists who were peacefully chanting just because they bothered his girl friend. Quark was fairly accurate in calling him a fascist.
So no, I really don't think Odo would've held it against Data for shooting Fajo who was a known criminal, even if he couldn't prove it.