Join Date: Dec 2006
Total Points: 494,563,588,968,328.06
If you told him through message then you did nothing wrong.
Though me and my friends tell each other things in person. We do not use facebook for that, especially for serious advice. If he's your best friend, confront him about it and tell him in a good tone what you meant. It's his son so that's why he's defensive about it.
Never use facebook, text, phone to tell your friend serious advice.