I'll give you that you should go into the shop with a clear mind and let them explain, but personally I'd be furious.

We're talking about your ability to stop which could cause a fatal accident! I had the bike shop change over all my bikes to have the front brake on the right hand and they didn't want to but they did it after my explaining why. It's more natural to me, it was after an accident and I didn't have full strength in my left arm, etc. If they felt it was a safety issue they should have spoken to you before changing it. This shows complete disregard for your safety and disrespect (in my opinion). I ride with my son attached with a tag-a-long and that puts multiple people at risk. I shudder to think...

I'd like to hear their reasoning. And I'm sure I'd give them a respectable piece of my mind.....