Could it be that the wording, "Remember, we are something to be revered." was referring to the intrinsic value that we all have as human beings? Even if there were indications that it was written by a thru-hiker, maybe the author's intent was not limited to that small audience.

As far as defacing someone else's property with graffiti, I also believe that Twigs '15 was wrong to do that. There may have been good sentiment and possibly even wisdom meant for everyone, but being presented in the wrong medium taints it.