>It's more likely that their changing needs/wants move that bar, than that the moving bar changes their needs/wants.
This seems to be an unsupported speculation. And indeed it cuts both ways. Maybe you only think the second house is ok because that covers your needs and wants (either present or future anticipated). If you leave out the psychologizing, there's nothing to your argument beyond the slippery slope. Even if the exact location where individual people draw the line is psychologically explicable based on self-interest and their particular life circumstances, it still doesn't follow that a moral distinction cannot possibly be made.
More generally, it's fairly obvious that people who believe in strong property rights will tend to be people who have lots of property and people who don't will tend to be people who don't. That doesn't invalidate the arguments of either side; these have to be evaluated on their merits. You can say "I bet you'll believe in strong property rights once you own a house!", while a homeless person might equally say "I bet you'll have more sympathy for squatters once you've lived on the streets for a year!" Those sorts of examples tell us that people aren't perfectly disinterested when forming their moral outlook, but it doesn't tell us much about where moral distinctions can or can't be drawn.
This seems to be an unsupported speculation. And indeed it cuts both ways. Maybe you only think the second house is ok because that covers your needs and wants (either present or future anticipated). If you leave out the psychologizing, there's nothing to your argument beyond the slippery slope. Even if the exact location where individual people draw the line is psychologically explicable based on self-interest and their particular life circumstances, it still doesn't follow that a moral distinction cannot possibly be made.
More generally, it's fairly obvious that people who believe in strong property rights will tend to be people who have lots of property and people who don't will tend to be people who don't. That doesn't invalidate the arguments of either side; these have to be evaluated on their merits. You can say "I bet you'll believe in strong property rights once you own a house!", while a homeless person might equally say "I bet you'll have more sympathy for squatters once you've lived on the streets for a year!" Those sorts of examples tell us that people aren't perfectly disinterested when forming their moral outlook, but it doesn't tell us much about where moral distinctions can or can't be drawn.