Yeah, poorer people can be elitist, but that doesn't necessarily make what McMansionHell is doing some elitist sort of enterprise. It's a guy/girl pointing out architectural flaws in buildings and discussing why they are flaws. It's as elitist as movie critic talking about a new film, and in that sense it's ridiculous that the site is being pulled down over this. You aren't entitled to have somebody agree with your taste.
Edit: You're right, nobody is arguing that it was pulled down for that and I didn't realize until I read a bit more. My point about entitlement still stands though.
I don't think very many (or any) people are defending Zillow's attempt to take down the site. Most of the critiques expressed in this thread specifically address the content of the site itself not whether it should stay up.
One big difference between McMansion Hell and media criticism in general is that the former relies much more on appeals to canon, e.g. "You should never put one of /these/ next to one of /these/."
Edit: You're right, nobody is arguing that it was pulled down for that and I didn't realize until I read a bit more. My point about entitlement still stands though.