As a combat vet myself and having retired after 20 years of active duty, I can understand the differences it makes vets feel. It once made me feel uncomfortable, but what I do now is simply reply with, "Thank you for what you do." Even though TYFYS has become such a catch phrase, you never know what kind of person is going to at least say "Thanks". I may not know anything about the person that thanks me, but just thanking them for what they do and being willing to make the words "Thanks" come out of their mouth is enough for me.