I also take pleasure in the so-called negative power in Grotjahn's work. That is I love his paintings for what they are not. Unlike much art of the past decade Grotjahn isn't simply working from a prescribed checklist of academically acceptable curator-approved 'isms' and twists.
It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. The other is mere business.