Sorry cannot see how your taxes subsidize his behaviour, lets not kid ourselves red diesel is not tax free. The oil companies pay large sums in North sea tax and we pay VAT. We are an oil rich country and it produces an enormous amount of revenue such that our use for leisure boating is but a drop in the ocean so to speak. Tax on fuel for leisure boating will not effect the guy in the gin palace it will hit the retired, boating on a shoe string guy who gets pleasure out of messing about in boats. Some have already been priced off the roads you are just voting these guys off the river, which would in my book be rough justice.
Do you like many others enjoy holidays abroad how many miles to the gallon of jetA1 do you think you are consuming at a lot less than Ł3 a gallon. Maybe somebody has the figures but I would say the polution from aircraft exceeds that from all the cars. So no I am not going to think twice about the very small amount of diesel I use in pursuit of my bit of pleasure.

Happy days!
Trevor