When an engineer get's all high and mighty like this the best thing is to remind them they are not engineers. They are technicians. The man or woman that designed the system and wrote the troubleshooting of it is the engineer, they just follow someone else's guidelines.
I don't even think your license says engineer on it any longer. The Germans protect the title of engineer from technicians. The man that comes round to fix my broadband is not an engineer. The Sky installer is not an engineer. The man that fixes my fridge is not an engineer and neither is the person who follows the maintenance manual that someone wrote for them.