[harleyquinn]

I think the issue here was that the worker was drinking Pepsi while delivering Coke (and therefore was probably in a uniform that identified him as a Coke employee). If he was fired for drinking the competitors drink outside of work, I'd agree he shouldn't be fired, but if he did it while wearing the uniform, and therefore was serving as a representative of Coke at the time, then they are in their right to say, "you are a poor representative of our company and it's values and therefore we don't want you out there serving as our representative".