Well how would you feel if it were your stand and someone eles climbed in it? I agree that public land is just that public, but the stand is not yours and you should not climb in it! But if it is a good spot and no ones there you can always hunt there but out of your own stand or on the ground,but you will have to deal with the fact that you know ahead of time that someone may show up to use that stand and be willing to accept how that will effect your hunt!
If we don't respect each other, how can we get the respect of others!