If that park water supply spigot is community property and not an on-site tap then sure there is ... it's inconsiderate. I've done this rarely and only if the tap was right in front of our site and only because I connected to it with a quick disconnect fitting so if someone else came along wanting water I could instantly disconnect to allow them to do so.
I like the way that you mention it being inconsiderate to hook up to a community spigot and then explain to us that you have done it but for some reason its okay because you have a quick disconnect LOL. If its a community tap it doesnt matter if its close to your site or not - dont hook up to it like its yours, pretty simple.