Those in the military are sacrificing their lives to protect our country. I think they should be able to use their discount any way they want to.
Sometimes people want to help but don't really have anything they can offer but their discounts. The business is kind to be willing to offer the discount, too, out of respect for their service.
Kindness has a way of paying it forward and we need lots more kindness in this world. Perhaps it was the patriotic clothing of the person in line that caused the thought of sharing the military discount. We won't know. I prefer to assume that it was just a kind act that was not intended to denigrate military service in any way.