There is quite simply no substantive or credible argument against the scientific facts supporting mans influence on the climate.
Those who foolishly debate against such overwhelming scientific proof, do so only because of fear. They are afraid that big business, as the primary cause, will be ordered to pay for mitigation at some point in the future.
The major worry for those who actually understand the causes, is that the two countries set to carry the greatest mitigation costs, China and the US, are entrenched in their refusal to accept the science, and represent a diffident majority of the worlds trade.