The generous skeptic
If you've got a big idea, there's no doubt that you will run into skeptics along the way.
Many skeptics are afraid for you, embrace the status quo, and in their twisted but well-intentioned way, will work to persuade you to give up your dream. This sort of skeptic should be ignored, certainly. It doesn't really pay to argue with them, because your impassioned restatement of your view of reality will do little to persuade them that you're not doing something crazy risky.
The other kind of skeptic, though, should be treated totally differently.
The generous skeptic has insight into your field, your strengths and weaknesses. She wants you to succeed, but maybe, just maybe, sees something you don't.