"A moral barometer is like a diploma or letter of reference. When you apply for a job, credit line, condo, etc, the manager (or whomever) is going to want to see your credentials and references. What's more, s/he might insist that the diploma/reference had been issued by someone/entity of high repute and veracity. So, when an atheist says "I have a moral compass" Our next question becomes: "And from whom were these moral standards established?"