Stealerships void warranties because they think that you'll pay them to fix your scoot. You'll pay more than the manufacturer does so their profit is greater and paperwork is less and they get paid faster.
Poor business ethics IMO. Unfortunately you call Suzuki and they'll seldom go against the dealership because it is less money THEY have to spend.
Best bet is to take your bike back, run the fuel out of it, put in pump gas and go to another dealer. IF you ever go back simply mention your grattitude for forcing you to go elsewhere because your NEW Dealership treated you GREAT and you didn't know how nice it could be to deal with a dealership until you were forced to go elsewhere. Mentioning taking a few friends there to buy bikes from them is always a good touch. This usually has the best effect in front of the store's GM or Owner.
It just MAY get this warranty denial stuff to stop!