Also, by your logic, Anakin was justified in trying to save his wife from death by killing the Jedi.
That’s… a bit of a reach, to say the least. Surely there’s a massive difference between (A.) betraying your brotherhood and massacring children, and (B.) killing the one person who has done the most harm to the Galaxy for decades.
But I do agree with you that Rey wouldn’t know all the details of the situation, including the transfer.