you cant sac in response. The vote is part of the resolution of the card. Much like how once you have named a card with cabal therapy it is too late to counter it.
God. Deep breath. Everyone please just read this card. You absolutely can respond to this spell (like most other non Split Second spells) with sacrifice abilities (assuming they are instants or mana abilities). When it resolves if the thing you were
probably going to vote for is gone then you can (must) vote for another non land permanent you don't control. If there aren't any non land permanents you don't control then nothing happens.
No need to get huffy. He's talking about the fact that you can't "fizzle" this spell. The thing getting exiled isn't selected until the spell starts resolving. So as long as they have at least two non-land permanents, you're gonna get something. From your post, it seems like you get that just fine.
This card is very good, very powerful. Probably not going to make it in Vintage, honestly. It reminds me of that one mana Boomerang they also put in Consipiracy; it's good, but Chain is just better.