Should veterans tip if their meal is free in a restaurant for Veteran’s Day?

We will assume that the service was good for this one.

Sorry for another tipping poll btw but I️ need to put this one to rest for my family lmao

So we have this family friend who served a party of 12, which were all veterans, and said their meals were entirely free. He said he put a lot of work into the table and was shocked when they told him that he did a great job but did not tip him. He’s let it ruin his mood for the day. His grandmother says that he should be thankful for veterans fighting for his life and that he should accept THEIR service as a tip to him just for Veteran’s day, but he is extremely upset about the ordeal as he says it happened with other veteran tables as well to his coworker and he says they should tip ESPECIALLY if the meal is free. He says he only made about $10 for the entire shift (I’m guessing he works at a place that a lot of Veterans like to go to for today).

What is your take on this? Should veterans tip on their free meal? Why or why not?