The difference between a troll and a controversial writer is that a troll cares about the point as a means to effect controversy whereas a legitimate writer cares about the controversy as a means to get the point across. 37Signals seems more the latter than the former.
If the controversy were a byline then the writer would have a "taste for" pushing their point though and merely be riding the controversy to get there.
IMO writers often care about controversy because they make money based on engagement and get better responses if people are passionate about the subject. I don't think this harms their legitimacy as a writer it just provides a poor motive. Trolls on the other hand want to maximise engagement as it gives them a sort of sadistic pleasure, they do it for free.
