Ignore values, because you're right, that's a wash. Different people value different things.
Consider the hard figures: dollars and CO2. Suburbs don't support themselves financially (unless we massively increase property taxes) and their carbon emissions per capita are way higher.
You're right that people are free to have their preferences and make trade offs, but we as a city shouldn't be subsidizing urban forms that leave us worse off. If you want to live in a suburb, fill your boots, but don't expect the rest of us to pay for it.
Also, keep in mind that until not that long ago, Edmonton's zoning laws very strictly limited where dense housing could be built. It's not just that people preferred car dependent suburbia, it's also that it was legally the only thing you could build a lot of the time.
They might not use the LRT, but we won't be using their endless roads and new rec centers. We'll also be making less use of the expensive highway expansions required to facilitate a suburban lifestyle.
Higher utility distribution fees from the new water/gas pipes, new schools that have to be built (even though there's plenty of space in core schools, new fire stations. Suburbs are mega expensive and don't generate enough revenue to actually replace their infrastructure.
In conclusion:
Suburbia is objectively worse financially and environmentally - I'm not imposing my values on anyone unless you don't value money or the planet. Given that, why should we be subsidizing it?