I think that when there is such a large conflict of interests, the best course of action would be ignoring opinion pieces on the parent company/owner altogether

I think that when there is such a large conflict of interests, the best course of action would be ignoring opinion pieces on the parent company/owner altogether. If it's major news that you cannot avoid publishing, just report the basic facts with no commentary. Otherwise you cannot really read the piece without entering a similar spiral of thought: "Is it genuine ?" "If it's critical, is it to make the point that the paper really is independent ?" "If it's positive, how can I trust it, considering the source ?" etc...