In California, many of the air tanker bases have viewing areas, complete with picnic tables, some with dedicated, fenced off areas with bleachers, parking, etc. It's not a spectator sport, but during times of high fire activity, a lot of people, especially folks who appreciated the older aircraft being flown would come out to watch. I always thought making room for them was very appropriate, especially considering they were taxpayers who had every right.
When things slowed, down, I gave hundreds and hundreds of tours of the airplanes, all over the country. I had a chance to meet a lot of folks with connections to my equipment when it was in public service the first time around...veterans who flew it during or just after the second world war. Veterans who would bring me boxes of pictures, souvineers, and stories, and who would cry when they saw the airplanes. I always made sure we had time to get them up inside to sit in the airplane and reminisce, when the chance came along. It was important for them, and important for me. One man and his elderly father chased us around for five days before he caught us sitting still for a day, and he brought us photos of two submarines being destroyed by our type aircraft. He old me a story about making a forced landing in one in Europe, and being so buried in the earth that he stepped out of his cockpit onto the soil...just below his window.
At one particular region 5 base (california) a young man used to regularly come to see us. He'd make models of the airplanes, tell stories, show us pictures he drew or that he had taken. He loved to see the airplanes. One day a pilot drew him aside and told him to get lost, called his mother, and demanded she come get him. The boy was mentally handicapped...he was proud of the watch he maintained over the four or five aircraft that routinely manned that base, and I thought that was just fine. I was disgusted by that pilot (who is now gone)...but he did have the legal right.
Truth is the kid wasn't hurting anyone. I only hope over time someone gave him another chance to hang out there. Most of the aircraft have since moved on to a decomissioned air force base, so there's not much to see (but a LOT of history still there)...I think plane spottes are just fine.
Now if the cops happen to stop by and see someone watching aircraft through the sights of a man portable missle launcher, then I think they're well within their rights to ask them to relocate to a better position...