It sounds like the place isn't just a guy's private home, either, but some kind of small apartment complex or shared home with tenants. That means it isn't just his personal concerns he has to keep in mind, but all those of the people paying to live there. Also means it's a lot harder to determine if it's someone who should be there or not -- it wouldn't just be his guests there, but his tenants' guests, and a lot of places keep security logs of that if it's in certain areas.
(I know one building I lived in when I was in Los Angeles sure as hell did.)
I'm mostly horrified by the people insisting the guy is a douche for not letting people on his property like he's the jerk.
Who is going to get sued if they get hurt there? Him. Who is gonna get sued if one of his tenants gets hurt because of people trespassing? Him. Who is gonna have to pay for the damages of people tromping through/extra groundskeeping/having to clean up when even less thoughtful people litter/etc.? Him.
I kinda can't help but empathize with this guy. We have two empty house lots (that now need to stay that way, thanks nature! Long story.) that we used to let the neighborhood kids play in for over thirty years, because that was just being neighborly. Until a whole lot of entitled parents decided it wasn't their fault when the kids broke my folks' windows playing, ripped up stuff my mom had spent hundreds of dollars planting, and started insisting the folks improve/add shit to the field to make it safer for their kids to play there. Yeah. People who wouldn't even fix the shit they broke were demanding the people who were being generous and nice should be the ones to lay out more money so they could continue to be taken advantage of. Like my retired, elderly, broke-ass parents are going to walk the property every two days looking for gopher holes to fill or pay a landscaper to fix so their kids can play on it and continue ripping the place up? I don't think so. (You would have loved the looks on people's faces when my father -- who is admittedly clueless -- suggested, "Why don't you just have the kids tell us if they find a hole, or one of the older kids can fill it in before they start playing?" You would think he'd suggested filling the hole with one of the little kids' dismembered bodies.)