After more study, I have some corrections and additions to my last.
1. The mere presence of pickpockets in your park does NOT trigger the "high crime" notification. You only get that if they're actually stealing, or vandalism is rampant.
2. Sufficient security,will totally deter both theft and vandalism. The 2 main components of "sufficient security" are cameras covering nearly every square inch of the park and a guard with a work roster keeping him at the park entrance. Roving goon squad patrols also help but aren't as important as these 2 things. "Nearly" every square inch means there's no more than about 5m between the FOV of 1 camera and the next. Pickpockets 1st spot a target at a distance and have to move up next to them. This usually requires more than 5m of movement.
3. The best way to keep a guard at the park entrance is to move the actual park entrance turnstiles into the park slightly from the default position, so you can put an entertainment point on each side of the entrance path just outside the turnstiles. These entertainment points must be in separate buildings so you can select them individually when creating the guard's work roster. This will make the guard pace back and forth across the path so his FOV frequently sweeps back and forth across it. This is important because....
4. Fleeing perps can be caught outside the park, over the whole distance between the turnstiles and the spawn point. And in fact you and eject pickpockets prior to them entering the park. If a guard catches a dip before the dip reaches the turnstiles, the dip will still go through the turnstiles, pay the admission fee, and then turn around and leave immediately
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5. Pick-pocketing begets vandalism. Robbed peeps get mad, and in general the more theft, the more the rest of the peeps feel like the park is anarchic and lose their inhibitions. Control theft and you'll control all or most of vandalism as well.
6. A very small percent of peeps in your park at any given time will be dips. But if you have sufficient security, they'll be completely deterred from stealing anything. They'll pace the paths constantly looking up at cameras and over their shoulders for guards, but that's it, until they eventually decide to go home. While they're in the park, apart from never going on rides, they act like normal peeps. They pay the park entrance fee, they buy food and drink as needed, they enjoy the scenery, etc. So deterred dips only really harm you in not spending very much money, and taking up 1 peep's worth of your park's capacity, thereby keeping out 1 mainstream guest. But on the plus side, deterred dips tend not to stay as long as honest folks.
7. Dips appear to function as their own new 4th demographic. They are always going to be a certain small fraction of the total peeps in your park. Because they're a fixed fraction, once your dip population reaches that number, you won't get any new dips until an old dip leaves (voluntarily or not). Therefore, it's probably better to deter dips than actively hunt them. For every dip you actively profile and eject, a new dip will spawn soon to take his place. But deterred dips are still paying customers, so having them in the park buying drinks is better than busting them before they go through the turnstiles.