Actually, what they're doing works just fine for them. They don't deny the OT, they just rationalize away any need to follow it. The fantastical stories were metaphors, the laws only applied to a specific group of people, Yaweh was such a prick because that's all the people of that era would respect, etc.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.
Albert Einstein
Albert Einstein