Here's my two cents. If my child were to ask me that question, I'd just be totally honest. My folks were always honest with me and let me have an imagination and let me figure stuff out on my own. Like Santa Claus. I figured out on my own he wasn't real, but my parents never stopped me from believing in him. Not telling you what to do but if I was in your shoes, I'd just be honest. You don't have to be brutally honest but be honest and let your kid figure out in his mind if it's moral or not and if he ask you your moral opinion on it, shoot straight, tell him what you think is right and wrong. What you do now in this situation will follow him for the rest of his life. I can understand you wanting to protect them from the big bad world, we all want to, it's a parent's instinct. But I really think honesty is the best way. Because years from now when he really understands what it means, he might not know where to stand and wonder why momma didn't just tell him.