I doubt you will make yourself believe that it is true.
With that in mind, think of what the negative side are going to say. Then, think of how those points are questionable. Is the evidence that accurate, is it biased, was the research not done THAT fairly? What's not so perfect about the points the negative side is going to mention? Can you really TRUST the information that is going to be mentioned?
Think up of questions that will question the opposing side and answer them. Now, you may be able to find opposing evidence to help you support the argument you don't really want to put forward. Chances are that's going to be hard but there's not a lot you can do but to get the debate over and done with.
Good luck and all the best.