I'd love to make Gil and buy my own home.
Too bad there's no homes to buy.
What you're mentioning is not the problem. The problem is that the thought process you're subscribing to either assumes an infinite number of houses, or simply doesn't care about people being locked out of certain features.
By buying multiple items of which there are a limited amount, you are denying other people of that item. Add into that the fact that those items allow for entry into content that people will otherwise be unable to experience, and people will be understandably frustrated that other people are buying multiple things of which there is a shortage.
It's not a question of jealousy. It's people being annoyed that they are unable to access content, regardless of eligibility, because someone logged in while they were at work or whatever and snapped up their second or third house, which would be of mostly redundant use, mechanically. This is not an unreasonable complaint.
The argument that people should not do so therefore stems from the following: Do you have absolute control over all the content you want? If so, then don't buy a second house. If not, then do. Living in an FC chamber does not fulfill that first value if you want unrestricted access to certain things. Having control over an FC house, meanwhile, does fulfill this, which brings into question why someone might buy a second house under that circumstance.
"Because they can and want to" is always a reason you can use, but that doesn't take away anyone's right to complain. I have the legal right to buy up every bottle of soda in the world and say none of you can have any, but that would still make me an asshole.
Also the bit about having personal rooms in a personal house is irrelevant, considering that a personal house serves all purposes of a personal room, and then some. No one raises a fuss about it because it would be a redundant feature.