Here's how you respond. "Can't you just hang out and not play volleyball?"
Volleyball = whatever they do for fun, whether it's skiing or football or rock climbing or guitar or knitting or video games.
At this point, they will likely respond with, "Yes, I do hang out without playing volleyball sometimes." And you will counter back with "And I hang out sober sometimes." Or they may contend that volleyball is not a health risk, but being intoxicated is. To this, you should either agree and say that you do many activities that are potentially dangerous, or you should point out every single way that one could possibly get injured playing volleyball. You'll wear them down eventually.