i think a mental separation is needed. the tag 4x4 is pretty broad. i don't think anyone has the same level of objection to peoples use of an "old landy" used by an outdoorsman for outdoor activities in moderation, as they do for the bright silver fuel guzzling tanks such as built by subaru, honda, etc, etc, and are being used by soccer moms to shuttle their kids too and from school. again, the problem caused by this type of vehicle in an urban environment may not be fully appreciated by those who do not currently live in, and have to navigate around a city.
yes, the legal system tends to tar everyone with the same brush, but it has to, to keep a semblance of justice.
...........and the attitude of "i pay my taxes, so that gives me the right to destroy a little bit of the world in any way i want to" is just as ignorant as can be.
and on an aside, h20 asked about veggie oil for running diesel engines; converting an engine is easy. it involves a filter for the oil, a tiger-loop to extract excess air from the oil, and a heat-plate to heat the oil for combustion. some people get their oil from the local restaurants and chippers, filter it themselves. in some areas you can buy bio-diesel.
other issues in the conversion are, your engine will probably need a little more attention and TLC after the conversion, and you may not get as much power and acceleration from your engine. then there are other variations on the theme, with two tanks systems, or oil and diesel mixes, etc etc. the biggest bonuses to conversion are, cheaper, (slightly) cleaner emissions, and your money is not going into the pockets of the petrochemical companies.