I find it to be an interesting point. While I can see where you're coming from in terms of the "customer is always right" approach, I think that your argument rests on the assertion that the product (in this case trousers) is ultimately trivial and of no consequence. If it weren't so easy to consider this persons product trivial, this would probably be much different. For example, if you took your car to a mechanic and asked for work to be done that would cause the car to not work properly, no one would argue with the mechanic for refusing. In the case of trousers it is more subjective, and arguably 'trivial', but maybe not to the tailor, because after all, this craft is the basis of his livelyhood. I think tailors have the right to refuse work if they feel the need to. You can always find someone else who might be willing to do it.