As I've just written on speed cameras, I may as well get this out of the way before the tabloids start encouraging the selfish bastards to start blockading roads again. So time to spell out the same basic economics.
Yes, taxes make up a large proportion of fuel price. But if we are to reduce tax, then we have a choice between lowering tax most for those who earn the least, or lowering tax most for those who generally drive the most expensive vehicles.
Taxing fuel rather than other things has other secondary effects such as discouraging urban sprawl and encouraging high street rather than mall shops, reducing traffic congestion while encouraging walking and cycling. Sorry about that.
There are winners and losers in every choice. But we should choose wisely.