I've been on the receiving end of this, but have never been denied a space. Most generally when I tell them it is a Prevost they say it is okay, but I have also had to tell them you can't really tell a '92 from a '99, so that would work for a few more years.
I can certainly side with park owners on this one as I have stayed at parks that got hung with some group showing up in a beater POS RV with a bunch of folks crammed in it looking to park cheap and hang out at the pool all weekend. It turns into a loud, obnoxious, free-for-all party that drives everyone crazy. I tend to stay away from parks like this, not because I feel like being a snob, but because if I were into this, I could go to about any public lake in Oklahoma or Texas that has camping spots and live thru the same hell.
And then some towns have laws that cause the RV park owners to deny older coaches. I have also run into this, but have always found a way around it. It's kinda like the security at the airport; I don't like the hassle, but the alternative is scary.