I think you make a good and very valid point. But....
Unless you know exactly where a picture is taken you have no idea if it is really "off trail". It could be on private land, it could be in a different country then the USA or it could be there is no trail, ie desert. I do recall, I would have to go back in the thread and find the posts, I posted a few pictures of one of my trucks flexing up on a rock in a wash down in Arizona. Now I got some flack for that and one guy says something to the effect of what you are saying, don't wheel off trail dude because it ruins it for the rest of us. I was in a wash in Arizona! As far as I know, having been told by my 4wd buddies who run large 4wd clubs in Arizona, a wash is open to all 4wds. There is no trail in the wash, as long as you are in the wash it is open game. Now I am sure there are some exceptions to this but my point simply is if you have no idea where a picture is taken you can't say if it is off trail or on.
I am a tread lightly kind of a guy, I won't poach a trail that is closed, I won't make my own trails and I won't wheel with people that do. I also clearly understand that having lockers and not spinning a tire means less damage to a trail or the enviroment in general. In my 20+yrs of offroading I have seen many trails close and do not like it one bit and do not want to be a part of what makes those trails get closed. However, I am going to wheel my trucks and if you don't know where I am wheeling then why say something about it?
The tree huggers and the people getting trails closed are going to use whatever they can be it some pictures from this forum or another forum. It doesn't matter if the picture is from a legitimate trail or not, they are going to use it to do us harm. I will even go so far as to say tree huggin nazis will use pictures not from the USA to hurt us. The way to fight them is not to scold a person for posting a picture you think shows off trail driving. I would think most people in the community understand this.