Was I being helpful? Or just interfering?

I had a falling out with one of the other managers today. I popped over to the supermarket and noticed that the queue in the café was incredibly long, and looking unhappy. The girl on the till turned out to be a 17-year-old who had only worked there once before and she was really struggling to come to terms with the till. Everytime someone ordered it took her a couple of minutes to work out which buttons she had to press, and there was no-one around to support her. 
I stuck my head through the kitchen door and there was one person cooking the breakfasts. So between the two of them they had to take the orders, cook the orders, deliver the orders and keep everything clean and tidy, and stocked. 
I went up into the managers office and the head of the café was sitting there with a mug of coffee, having a look at the betting odds in The Sun.
I said “I think your staff could do with a bit of help downstairs”
He said “Nah, they’ll cope. How busy can it be at ten thirty on a Friday?”
“Pretty busy actually. How come there are only two of them running the whole show?”
“Benji called in sick. Got flu for the third time this year. Couldn’t find anyone to replace him.”
“Well I think you should try a bit harder, they’re drowning down there.”
He looked up from his newspaper and said “Why don’t you keep an eye on your own department, mate, and stop sticking your nose into mine?”
I said “I don’t need to keep an eye on them. They’re properly trained and there’s enough of them to cope and they know they’re always supported.”
“Well bully for you. Personally I haven’t got time to be holding the till girls hand every hour until she gets the hang of it.”
“No I can see that. You’re too busy planning who to back in the 3.15 at Kempton.”
Then he swore at me and stormed out. But I did notice when I went downstairs again that there were two extra staff in the café and the tearful teenager was back behind the scenes.
I have a feeling there might be a complaint coming my way, but I don’t care. What’s the point of being a manager if we’re not going to help look after all the staff?
Maybe I wouldn’t have been so grumpy about it if my ankle wasn’t sore, but I still think he deserved it. 

RC 29-6-15