I don't think it's an editorial stance any more than deleting articles about Microsoft and keeping the ones about Apple and Google is an editorial stance: HN has a long-standing policy that if a thread becomes hostile and devolves into a flamewar, it's removed from the front page.

Unfortunately, any thread about Microsoft quickly devolves into a flamewar. Similarly, any thread about politics, especially one that can be brigaded from other places, will quickly turn into a flamewar.

It's not that dang (et al) remove just because they want to, they remove because it becomes toxic. They stay up and in place long enough to know that.