HereForTheBeer: Coming in with the attitude that it's pointless to put one's games elsewhere, I assume they really don't give a rip. Pissing off a customer base they don't cater to in the first place isn't likely to cause much of a dip in sales.
There's one universal rule that he should consider though - not to burn your bridges. Phil Fish did, and Fez sold pretty poorly as a result on PC (across all PC platforms, before anyone starts making comments).
I'm sceptical of his claim about his success on Steam - according to Steam Charts, it's barely averaged out at 100 - it peaked at 500 in February, precisely at the time that he had the game in no less than three indie bundles and on IGS. That's not a great figure barely four months after release. In fact, it seems most of the traffic came post-bundle.
Even developers more reluctant to follow the DRM-free path have used it as a back-up revenue path later on - the non-Steam DRM-free market is not to be ignored, and a lot of devs are realising this (Harebrained, Humble Hearts etc.) There's an entire market out there that doesn't buy from Steam at all, and PanicArts has managed to isolate itself from that entire market.
But I'm just going to ascribe this to him and his ilk being spoilt little manchildren. The other Finnish guy he seems to be all buddy with ("Teroil Corporations") decided to put the wholly mature "GOG more like cock", to which Viglione responded in Finnish with a smiley (I don't speak Finnish so I can't tell what it was, but it's a safe bet that it was some kind of agreement).