The best idea can still die when naysayers raise concerns, even if the concerns are meritless. Instead of trying to dodge unavoidable attacks, learn to expect the common types you'll face, and how to counter them simply and convincingly:
Confusion. Detractors often present distracting information or try to link your idea to several others in an attempt to confound people. Be clear about what your idea is and what it isn't.
Fear mongering. Nothing kills an idea faster than irrational anxieties. Know what fears your challengers might stir up and be prepared to allay them.