I think that it would be difficult to be a proper columnist because of the reactions of the people who you write about unflatteringly. Pure honesty compels one to be as straightforward and, well, honest about a subject. And, often, that means that said subject (or, as has happened more than one, people that assume they are the subject when they are not) has their feelings hurt. It’s even worse as a blogger because the medium is disrespected as amateur and the posts generally characterized as biting even when they are meant not to be.
Is it better to not write at all?
Or maybe that is the reason so many people choose boring subjects or direct their venom at inanimate objects like systems and society. They’re unlikely to get complaints or hear through the grapevine how hurtful they are.