Child discipline.

My in laws live with us and I’ve been trying to keep the piece and be as patient as I can be with them. I understand they are now comfortable but I’ve been noticing lately they correct my son over me. If he does something naughty and I am correcting him for it they will also correct him while I am disciplining him. For example last night my son stacked these plastic chairs from his craft table and climbed up and was sitting on them I turned around and yelled out of panic (because he scared the crap out of me) and ran over and got him down. As I was explaining why he couldn’t do that my FIL is yelling from the other side of the room at my son. I turned to him and said “I got it!” And he stopped talking. But am i over reacting? There has been too many times that this happened to even count. When it comes to someone else (family) correcting your children, what is acceptable?