Your dad's guilt trip is still working on you. I'd imagine if you put some feel into a swing piece, you would probably feel a little dirty for having done so. That, or you'd feel like a sellout to the "real music" community. If it makes you uncomfortable, don't do it. There's plenty of other music around to play. If someone else in your section can do a jazz piece justice, I can't imagine the conductor still wanting you to play it in an unwilling, wood-like fashion.