If Lore had been a human being, Data would never have done what he did to him. End of story.
I seem to remember a certain art collector that Data was attempting to "deactivate."
In disassembling Lore, Data (and the Federation) were simply returning him to the state in which he was found.
Several people have noted that Lore was found disassembled, and have tried to use this as some justification for doing it again. Remember when the Enterprise crew found those 20th century humans frozen on that pod thing. Now, they brought them back, but does that mean they would have to right to knock them out and freeze them again? Certainly not! That's like saying every parent has the right to kill their kid because they gave them life. Also, Data was found disassembled and was put back together by starfleet. Do they have the right to take him apart again as soon as he starts acting up? Perhaps...after a fair trial.