Honestly, "fooling around" isn't sex to me either. Touching, kissing, hand jobs, and dry humping are just not sex in my head or my heart. Which lead to no amount of trouble with Runic Wolf in the beginning. Hell, I don't consider blow jobs to be sex unless you're 69ing. Sex in my head involves both partners being equal participants in providing pleasure. And no, I don't consider masturbation sex either. That stuff is foreplay, foreplay isn't sex. Sex is what you have after foreplay. Does that mean I don't believe you need to be safe during foreplay, ofcourse not. But don't feel that you need to educate your boy out of his beliefs. They aren't necessarily wrong. You just need to be considerate of his definitions as well as your own.
I enjoy BDSM myself and don't consider that sex either, though I do orgasm during some of the things we do.