Well, I suppose it isn't, because he does stuff like that. Just goes to show of how little consequence he is that he has to do those things to keep himself amused during a war
See, this is another view derived from the show, that isn't like that in the books and just makes Stannis look worse. On the subject of sacrificing Edric (who is replaced by Gendry in the show), he keeps opposing Melisandre (as the only person who is not willing to burn Edric) and even asks her 'is there no other way?' and tells her 'if you lie to me, I'll have you killed slowly.' That's how opposed he is to killing Edric, and how little in thrall to Melisandre (who is also far worse on the show) he is in the books.