I had an entry under my soon-to-be-indispensible Underground DSM-IV which noted that "when someone challenges your credentials, no credentials will be good enough."
I am expanding that to a general rule for life. If you are in an argument with a socialist and say "I used to be a socialist," the demand for your credentials means the discussion is over. If you are arguing about bridges and say "I have a degree in engineering," it will not be the right kind of engineering somehow. Even if it is, and you've been designing bridges all your life and won the "Best Bridge Design" award 3 years in a row.
Today's was "I work with the poor." Well, a lot of people work with the poor, at least part of the time. Merchants work with the poor. Lots of government officials work with the poor. The police and ambulance folk work with the poor. It's not that odd, really. But when someone wants to make a point about the poor - as I did on two blogs today - facts can't be allowed to get in the way.
I don't claim expertise in most of the subtopics about poverty. But sometimes people make assertions that anyone who works in the biz knows to be untrue. Experts can go wrong in many ways - usually by getting some particular set of ideas in their head and fitting everything into that box. Credentials aren't everything. But taken with proper humility, they should mean a little.