4x4s aren't uneconomical per se, and it's disingenuous to wibble about "gas-guzzling 4x4s" when something like an X3 gets similar fuel economy to a regular family saloon.
Tax gas high enough, and people will become unemployed. The whole "raise fuel taxes to get people to go to work in bio-diesel powered buses" idea is an attempt to wish things into existence. Joe Schmoe on the M25 in his Pug 205 quite simply cannot afford anything else. LPG cars are expensive. Hybrids are expensive (and crap).
No-one needs a Hummer. True.
No-one needs a 10mbps internet connection, either. I've got one, though.
4x4s are annoying for a zillion reasons (owned by idiot drivers, can't see over/through them at roundabouts, noisy, ugly) but I wouldn't ever stop someone from owning one. I'd reserve the right to call them a cock for buying such a stupid vehicle, though.