Lord have mercy, who cares if someone wants to dip their feet?...Let's sit back for a moment and consider that putting your feet in the WWII pool is not disrespecting anyone.
The committee that represents vets that funded and constructed the memorial don't want you putting your feet in the water and there's a sign asking folks not do that. They care. How is it not disrespectful if you do it anyway?
It's like going into someone's home, having them ask you to please take off your shoes at the entrance and you say "that's a dumb rule. I'm not going to do it". Or, say, visiting a mosque and not taking off your shoes or visiting a cathedral and not following their rules regarding appropriate attire.