How do we know that he wasn't motivated by a sincere desire to enlighten the customer and potentially save his/her soul? If people don't hear the Truth from Traditional Catholics, they are unlikely to hear It from anybody else. We have an obligation to speak the Truth, even if it is inconvenient.
I don't believe this is a case of "casting pearls before swine." Until we attempt to inform a person of the Truth, we don't know if they will be receptive or not.
I agree that he violated his terms of employment, but I would argue that the time is nigh that all of us will have to do the same if we want to choose to follow God instead of Mammon.