McGuire will miss Friday's play-off semi-final against Wigan after being found guilty of a reckless high tackle during the defending champions' 27-20 win over Catalan Dragons in Perpignan last Friday.
"We considered an appeal," McDermott said. "There was a bit of merit in doing that. But we thought they gave us a fair hearing. I felt we put up a good case and I think it went as well as it could have done. If we did anything, we probably got it down from a two-game ban to one game."
McDermott, believes comments by Wane, in which he compared the incident to a tackle that earned Wigan hooker Michael McIlorum a three-match ban, were out of order.
"Unfortunately, with what's been said in the media building up to it, it would have been a tough call to not ban him. I'm just not sure that in any legal case you'd be allowed to say what you want in the media building up to it."
McDermott expressed fears the verdict could have serious repercussions for the game, with players fearful of going wholeheartedly into tackles in case they result in a fine and a ban.
"At the moment, players are concerned about going into collisions in case they get it slightly wrong," he said. "That's scary for our game. The beauty of our game is that usually, if you run harder and tackle harder than the opposition, you win the game.
"Now, if you run hard and tackle, you worry about getting a ban. Maggsy gets run at every single week by teams that try to exhaust the leading tryscorer in Super League.
"Because of that, Maggsy has to be aggressive and sometimes he gets it wrong. He hasn't the best tackle technique in the world and never has had but he is tenacious and competitive and sometimes that goes wrong.
"To judge him on one error, saying you got that wrong and it's a one-game ban, is very harsh. It's too clinical and I think if we carry on with this philosophy, players are going to start coming to coaches and say I can't afford to tackle hard."