Some people are NUTS!!!

[very-near]

I agree, it gets me when the rain is lashing down and visibility is poor, I am doing 55/60ish on the motor way and cant talk to passengers as i am trying to concentrate. I drive a big heavy 4x4 car that by all accounts is well equipped and safe (ish) in those conditions yet you still get the odd one or two pelting past you like your standing still. Its usually in cheap/old cars that are built for half the speed with half the breaking ability or road handling they must be slipping all over the place on the skinny tyres.

Do they just have no fear of their (or anyone else's) mortality?

I can't say I agree with this. The extra mass of a big car/van/lorry makes it a lot more difficult to scrub off speed. My car weighs just under 2.5 tonnes, and has some pretty wide tyres on it (265/70/15 IIRC).

 

[Over The Hill]

I agree, it gets me when the rain is lashing down and visibility is poor, I am doing 55/60ish on the motor way and cant talk to passengers as i am trying to concentrate. I drive a big heavy 4x4 car that by all accounts is well equipped and safe (ish) in those conditions yet you still get the odd one or two pelting past you like your standing still. Its usually in cheap/old cars that are built for half the speed with half the breaking ability or road handling they must be slipping all over the place on the skinny tyres.

Following from thread above - you may find that:
Being heavy the mass will more readily want to travel in a streight line when you want to go round a corner.
Being heavy it is putting more demands on the same area of contact with the road and has more mass to stop (most 4x4 have a longer stopping distance)
If it is a Range Rover or that type it may not be NCAP tested and probaby is much worse than a car or car based mpv in a crash (Espace v Range Rover = Espace won)
Handling is mostly about braking (that is when you tend to not go where you want to) and all cars are 4 wheel braking. The fact that you are driving 4 wheels is mainly immaterial until you go off road.
The extra weight counts as much against you in a crash as for you (hold a heavy book over your head and jump off a chair).

All in all you should allow for the poor safety, aged and inappropriate design, bad handling and braking of such vehichles and drive them more slowly.

(And, if as most I see around, just use your fog lights when it is foggy)