I'm angry at an old family friend for being obnoxious at my son's third birthday.
Are you going to tell him that you're angry?
Yes, I'm going to let him know the next time I see him.
I think you're right to be angry at your family friend for the way he behaved at your son's party.  Acting inappropriately made the party worse, and could have seriously upset the children. He shouldn't have acted like he did because messing up someone else's party is terrible, especially a birthday party for a child.
I feel like you're not taking my side.
I thought it was pretty clear that I was totally on your side, but I'll try to clarify.  It's okay for you to be angry at this family friend for the way he acted at your son's birthday.  Because this could have seriously upset the children, I think this person needs to be told that his actions were inappropriate.