You make a very interesting argument, it's true, most of the carbon we are pumping out of the ground used to be in the atmosphere. At that time the world was a much more temperate place according to fossil records.
"Scientists" claim weather is deteriorating as the climate changes, we've only been tracking weather for less then a hundred years, I'd like to know how they can say this without more evidence.
A far as carbon taxes being added to gasoline prices, it might reduce consumption a bit for awhile but the economy is only going to adjust for it. The main benefactors of course will be those who find a way siphon money off in the implantation of this tax through administration, auditing, policing etc.
If you go way back to the original post, he is right, all the pipelines and projects proposed for the tar sands is for export at discounted prices, while the oil travels right past points in Canada that are importing fuels at world prices. We should keep this raw product at home and export what's left over.