The trouble with identifying a single "product" that you believe we should be paying less tax on is that it doesnt really matter what item you pay the tax on.
Ultimately the government have an amount of revenue that they have to generate in order to provide the services they have promised to provide and pay off any debt.
Whether they generate that from fuel , tea bags, tobacco, or chocolate flavoured fudge is irrelevent. They need to collect it from somewhere so ultimately everyone needs to pretty much pay this amount of tax each year.
Fuel is an appropriate way of sharing this tax burden across almost the whole of the country - since everyone uses it (people who use public transport are ultimately paying for the fuel in the price of the ticket purchased)
They also need to ensure they collect the taxes - so taxes are levied on items that everyone either really wants - or cant do without.
Now I'd love to be paying 50p / litre for my fuel - but I would then not be too happy about a 15p rise in (example only) in the rate of income tax to cover this deficit.
Tax on fuel is also something we can all have a little control over ourselves - we can choose to drive smaller engined cars, hybrids, walk for short journeys or operate car-shares. There are not many other taxes that you can effectively change the rate you pay yourself.
Boycotting single suppliers will not affect the amount of tax paid to the government - since we will all be paying exactly the same amount of tax if we use the same amount of fuel - where ever we buy it.
Theres also the fact that Tescos / Asda etc do not produce / refine fuel themselves - where do you think they get their supply from?
I buys my car - I pays me monies.....