Please heed the advice of missional-minded Alan Hirsh (who got toasted by some political conservative Christians on his blog for expressing a choice different than theirs) when it comes to voting:
Choose my friends! McCain or Obama (they are both good men as far as politicians go), but do so in good conscience before the Lord and, please, grant others their right to differ.
In terms of how we communicate our opinions, well that’s back to the question of civility without which civil society cannot function. We are Christians living in a democracy…lets be gracious to each other as the lack of grace for the disciple is a greater sin than simply expressing a wrong opinion.