I’m with Hora on this one. I’m all for folk enjoying a bit of fun in the outdoors if they want but only if thye’re discrete and a long way from other people. I’m far from a prude but they don’t half make you feel uncomfortable. I’ve had issues with them on a few of occasions, including turning up at my local beach, going kitesurfing then coming back and having to drive home in my wetsuit because the locals were driving up and looking through my car windows (and not just glancing, properly staring with their bits out) while I got changed. I thought there were rules about flashes of lights to get people to come over etc, doesn’t seem to apply anyway!. And the same as the OP – local trail-head car park getting over-run by folk wanting to get their end away so much so that local older folk no longer want to go for a quiet walk in the evening in their local beauty spot.
As with cars and bikes on the road, people should live their lives in a way that causes the least impact on others possible. Having a ham shank in the public car park and approaching strangers cars at the beach to see if you can masturbate over their window is NOT minimal impact.