Romney's remark was made in private to a group of donors, not to the public. It was just about where their money would be spent in advertising. It's no different from Obama's writing off middle-class white people a few months ago -- just a different target group to direct their ads to.
Remember that Brooks has not been a conservative for a long time, and Peggy Noonan also wrote off Sarah Palin as "too conservative and religious." Make up your own mind, and don't put too much stock in journalists who are selling prose.