I agree on the morality points. But the interesting thing is that this isn't true:

> It enriches homeowners

Homeowners own the land, not just the building. If your property is worth X dollars when anyone buying is only allowed to (re)build a single family home on it, it must be worth more if they can also build a tall condo complex on it instead. Dense neighborhoods almost always more valuable on a per-unit-land basis than less dense ones, so upzoning is going to increase land value, lining the pockets of incumbent homeowners. This all makes perfect sense but everyone seems to go around pretending the opposite.

Now what does happen is that poorer people will live in these condos and apartment buildings, and send their kids to the same schools as incumbent families, use the same services, etc. I strongly suspect that's why people are so against upzoning, and I think that is an important moral issue in itself.