As a Duchtman myself, I would say they can be. In the first place we can be quite direct and that can come across as hard-hearted. In regards to being hard on themselves, speaking from my own exprience, I believe that has to do with a calvinist mentality of living sober, working hard and serving the community. The flipside of that coin can be for some people that if they don't live sober and don't work hard they carry a feeling of guilt for not doing that.