What is disgraceful is the chaos of the situation. National Parks have rules and they either need to be changed or enforced. If we are going to allow Mexican Nationals to enter a National Park and leave things for sale on the trails then change the laws to reflect that. Currently we actually spend money to hire people to do nothing. What a waste. Plus it makes the Mexican Nationals breakers of US laws and subject to penalties. If we are going to allow them to put things on trails then organize that so it can be done safely.
On the other hand, I don't remember seeing things for sale on the trails in Yosemite, Yellowstone, or Glacier. So maybe allowing people to put commercial items in areas that are supposed to be wilderness is not a good idea. In that case we should take whatever measures needed to keep pollution off the trails. A fence seems like a good idea to me, and people who actually eject people who put things on trails that are not supposed to be there.
With regards to the National Park I see this as a no litter and wilderness issue and not a political one. I volunteer at a State Park and we have Rangers and volunteers that actually enforce the rules. The park I volunteer at is only 15 miles north of the Mexico border.
As far as all the other blah blah on immigration. Order is better than chaos. Chaos leads to anarchy. The immigration situation is definitely chaotic at this time. If people obey the rules you get more order and more peace and quiet. If there are bad rules, change em.