Is it really that black and white though? I think we can all accept that torture is wrong, however this is still a generalised statement, and only the specific situation determines good and evil. So the more relevant question might be: could that cutting off of that terrorist's ear have been an STO act?Yes, I think the danger here lies in justifying the torture because it is done to the other 'team' and thus a black and white way of thinking. If one falls for that argument, then 'they' have succeeded in getting people to accept torture as being ok. When it isn't.
Suppose that act of apparent brutality sent a 'message' to other potential terrorists that will result in fewer terror attacks or participants, which will result in the saving of lives. Can we be so quick to judge? We should remember that the powers that Russia is fighting against murder and rape children in a deliberate, organised way, and are the puppets of even worse powers that slaughter and torture humans on an industrial scale.
Personally, I don't think that such a brutal act was likely to be anything other than STS, and while it would be nice to think that Russians are such ethically perfect people they would never indulge in an animalistic impulse for revenge, the reality is that everyone makes mistakes, and to be impartial would mean holding Russian security forces to the same standards as western security forces. In the latter, we have a clear historical pattern of aggressive, brutal and egregiously criminal behaviour - including torture - internationally, while the former has tended to focus on domestic order and their own 'backyard'.
So if one small participant (or group of participants) on the Russian side occasionally reacts disproportionately to the Anglo-American attempts to wholesale dominate and destroy them, I for one am okay with that, provided the overall direction and momentum of the greater good is preserved.