I am not sure just how to respond to your comments. I am assuming you meant the GM in the first sentence because the term "manager" used without qualification almost always refers to the field manager as in Gibbons.
With this in mind, there are some who will take a stand that you never trade within your division however I am not one of those. It depends on being able to get the most value out of your asset while balancing the negative aspect of having that asset in a rivals camp.
By the way, who did Anthopoulos trade to a rival that lead to this WS? I don't think you could be referring to Farrell cuz he not only failed as a manager while with the Jays but he was also not a loyal person AND he did not want to be here. If you keep someone like that on a team then their performance most likely will become more of a disservice to the club while creating a lot of discord within the club. Also, the manager, by himself, does not contribute to more than a couple of wins over a season and it was not as if there were other clubs to trade him to so that point is really moot.
A lot of people rag on Anthopoulos but that job is not an easy one. There are 29 other GMs all hoping to build the best team possible while dealing with multiple variables which has a direct impact on the make-up of the team. Anyone can sit back and crap all over the GM with respect to what move should have been made without having insider knowledge surrounding the possible trade elements - the fit (need/talent/health/personality of the player) for both teams, the value attached by each GM to the assets on both sides, the asking price (most probably based on talent evaluation), the resources (other players/budget) available etc. to name a few of the variables. It is not an easy task lining up those unknowns especially without knowledge of what's being offered so it is easier just to say he is not doing his job well cuz we do not like what we are currently seeing.
Anyway, we do seem to have different views on this subject.