The feeling of guilt when playing simulations which cover war machinery is a sign for a sensitive consciousness. It is not a bad sign or has anything to do with a trauma. I thing it is very natural if you really think about what you are doing in the simulator (what you are supposed to do). The reason for playing sims like A10c can differ very much. For one it is the pleasure of controlling one of the most complex "games" on the market. For others, like mentioned it is the pleasure to feel like or to "be" a soldier for a limited time at leas in your own imagination. What you experience is the result of questioning your own reasons for playing simulations. The question why you do that. What do you get from it. As silly as it sounds: What are you really doing during playing the Sim? This search for a reason in enjoying a Sim may show, that your other parts in Life may not be as reasonable to you as you would like to. Just a guess. As far as it goes for the bad feeling, there is one thing left to say: Your acting is judged by your purpose. You don't have to feel bad for learning a complex military system and stuff.
Hope it helps a little. Good luck!