I don't know what a real pilgrim is , I know that people claim that this or that behaviour indicates that is the mark of a real one but I find that the walk/pilgrimage is a process that brings out the less complicated and more in tune self, but the person on the donkey looked an idiot, she may be a very nice person but it was not one of her finer moments.
I will have to go and knock on my neighbours doors and tell them to to put no climbing signs on their fences, I don't see how they could have been so blind not to put them up in the first place, its obvious that any passer by was within their rights to climb over them as they wished.
There is no equivalence there. Your neighbor's fence is private property. The very existence of a fence is to mark the boundary of private, or otherwise restricted, property, rendering a sign to that effect redundant. If you scaled that fence anyway, you would be trespassing on private property. That is generally illegal.
Public artwork is on public grounds, and is generally quite sturdy. It is unfenced. It is subject to pollution and all weather conditions - snow, ice, hail, rain, lightning, heat..... It is subject to the whims of wildlife. Birds may perch and poop on it. It is subject to people to people touching it, embracing it, having their photo taken with it..... If there need to be restrictions on that access, then it should be fenced, and/or signage should indicate its fragility. In the absence of that, the default is that it may, indeed, unlike private or museum artwork, be touched.
It is fine if you choose to not approach, touch, or climb on the public artwork. If you think someone else doing so looks silly, even "idiotic", that is an opinion you are entitled to possess.
But I think it is far, far sillier, to declare that playing on or around the public sculpture on the Alto de Perdon is somehow disrespectful, or an affront or insult to Spain and the Spanish people.