I read in the Toras Avigdor pamphlet recently from Rav Miller Zatsal that the idea that Frum Jews are not honest in business whereas non-religious Jews are more honest ( I am not referring to MO but to non-religious – but it is a similar idea that the frum are not honest), is slander and calumny.
He related a personal story when he took a cab and the non religious Jewish driver was railing against frum jews during the trip. When the cab got 10 minutes away from Rav Miller’s house he turned off the meter. He said ” That’s enough money for the boss.”. It never dawned on him that is stealing.
Only Jews who learnt Chumash, the 3 Bava’s and Choshen Mishpat know the severity and definition of stealing.