Wow! I can't believe the nerve of some people. I would NEVER go on someones private property. The first thing that came to my mind when I read these stories about people picnicking in pastures with horses, is the palomino stud colt from the documentary BUCK...having a picnic in his pasture surely would've taught them a lesson.
Nightside, You're a lot braver than I am, I would've been too afraid to go confront them. I hope those people don't cause you or your animals anymore trouble!