If the equipment was designed for a child and you're 170 pounds then an officer might not side with you. However if someone is harassing you, politely ask them to leave you alone. If you're not causing a disturbance, endangering any person or property or damaging anything, then their harassment is a breach of the peace and is the only infringement of law. Being extra polite in a situation like this will really work for you and may end the problem. Keep communication to a minimum, polite but brief. As a last resort call the cops before they do. You can call 911 and report the harassment without requiring an officer attend. In Colorado Springs (El Paso) you are highly unlikely to have an officer attend due to the stretched budget this year. So unless there is a imminent threat f physical harm no-ones gonna come. Just state you wanted to report it to the record so in the event the harasser decides to escalate it into something physical your location is on record for a more efficient response buy the PD. 911 will make a report and you've done the right thing. The harasser will back down or get their friends. Either way the call to 911 is a good thing to do.
Getting in their face about your rights leading to a loud or violent confrontation would feel better at the time but would the worst thing you could possibly do. Bad for you, bad for the reputation of your sport.
If you're on private land and are asked to leave. Leave immediately, no option on that one. As a non parkour participant I can tell you it is perceived as a pretty dangerous sport, which opens up liability to the landowner by allowing you on to their property. As most buildings are privately owned you're going to have issues with being asked to leave. Banning parkour is a bit tricky as when does running and jumping become parkour? You can't ban a person from running so asking someone to leave your property is not ambiguous. Think of it from their point of view. Why would they let you jump on/off their stuff and risk possible injury and lawsuit. A signed disclaimer might help but I'd be very surprised if someone responsible for a government building like a school, would give permission. Possibility a private building like a mall, but even then it's easier just to play it safe and say no.
You have the right to use a public space and, again, if you're not causing a disturbance, endangering any person or property or damaging anything you have the right to do as you please.
(This is not legal advice!!)