The bottom line is the crap isn't yours, don't take it. Period, end of story.

If it is illegal and you feel compelled that you HAVE to do something, report it to the DNR, or CO and let them do their job. If it is on private land report it to the land owner. I have been hunting on private land and been told that if I see another stand to take it down. I have told the land owner that I am not comfortable with this, because I don't own the land and the owner may come upon me as I am taking it down. If they aren't afraid to trespass who know what else they might do. What I would do is to right a short note stating that the stand was there illegally and would be removed if they did not do so, and put it in a plastic bag and attach it to the tree. 9 times out of 10 the stand disappears shortly after that.