Well, if we're discussing morality, it is generally considered immoral to enrich yourself at the expense of the public good.
But it’s not a public good. .com stands for commercial. It’s literally the opposite of a public good.
Allowing people to pay a fair price for the resources they need to start a business (rather than paying scalper prices to the bridge trolls who got there first) serves the public good. “For the public good” includes more than just feeding blind orphans.
“chattel slavery isn’t bad so long as I am the slave owner”
A bit strong to compare domain squatting with slavery don't you think?