Like the others, I don't think this is trivial, since it demonstrates a lack of respect to you and your possessions, in your own home. I would have to know if this was just a one-time event or if his general attitude was this way. For a single aberrant incident I probably wouldn't say anything or treat him differently, except maybe watching to see if it was becoming a pattern. If it was already a pattern, I would be seriously considering whether I wanted to be such close friends with someone who didn't respect my boundaries.
If I wanted to say something to him about it, I'm not sure what it would be, though. Maybe something like, "Look, I just need to tell you that what you did during the knife demo wasn't cool. The next time I tell you to stop destroying my stuff, no matter how silly you think it is, you need to listen to me." Maybe stop there and see what he says, being ready to follow up with, "I don't care about the actual piece of paper. I care that you destroyed something of mine, in my house, even though I told you to stop. That's not going to happen again."
If a "what's the big deal?" person is actually a decent person who just never thought XYZ was a big deal, I think reframing the incident to reflect how you saw it can be really helpful to them. "Okay, what you did right there? To you it was just cutting up a worthless piece of paper. To me, it was ignoring me when I was telling you to stop doing something destructive with my possession, in my home. Which makes me wonder what else you think it's okay to ruin that doesn't belong to you." (Not necessarily what I would actually say, though.)