Since I live in a country that doesn't allow you to carry a gun wherever you want I know my view on this is skewed, but I would certainly be offended if I were to move to the US and find out that a contractor came into my house with a gun without my knowledge. I would certainly not be hiring that company again.

Now if the contractor I hired informed me that some of their employees had the proper permits to allow them to carry a gun prior to the work starting it would be different, however I would most likely request that they leave it within their vehicle or at home. I am certainly not anti gun, but they have their purpose and to carry one onto a job site isn't one.