I'm not even going to touch the rediculousness of this topic, as everything has pretty much been said. I will share how my parents handled the question.
When I was 9 or 10, we went on a family vacation to cape cod which included a day in Provincetown. (I can imagine the right-wingers reaction, Children shouldn't be allowed in P-Town! They will be scarred for life!) I remember we were on the beach when I saw 2 men holding hands.
Me-"Daddy, why are those 2 men holding hands like that?"
dad- "Because sometimes men have very special friendships with other men instead of women"
me- "Like how you and mommy like each other?"
dad- "yes, just like me and mommy"