He asks a very legitimate question. When we take a step back and drop our partisan pretenses we can recognize that politics is about winning, and you shape your message the best you can to achieve those goals.
I'm friends with two guys who run political campaigns in SF. When sitting down and talking with them you see the onion peeled back. They are ruthlessly concerned with one thing, winning. We on this board, and people all across the country, almost lionize the two political parties as some sort of deity. On the inside it is nothing of the sort.
Political parties choose messaging they think will appeal to voters. It doesn't mean they believe it.