There is no harm in gay marriage. The only arguments against are slippery slope arguments or argue with a religious basis; but I guess you have no problem with that, being a skeptic and everything? Oh, wait.
How do you rationally assess that there is no "harm"?
Did you just ask that question? Seriously?
Global warming, war, economy...
Just about everything the public takes seriously...
The public takes psychics, astrology, faith healing, dowsing and other paranormal beliefs seriously.
Are you seriously going to say that no political issue can be helped by rationality? Wow. Just seriously. Wow.
"Helped"? What is your argument? That politics should only be about issues that can be determined rationally, or helped by rationality?