In what way could Merlyn betray them? Malcolms motives are pretty much clear. He wants to kill brick, and they need all the help they could get. My point is, they had a common goal, so Malcolm had no incentive to pull his regular bullsh*t. All the team had to do, is stop Merlyn before delivering the final blow. And lets say they fail to stop him from killing Brick, is that really that bad given the circumstances? The man's a nut who, as was made clear, does anything for his own power, why not USE Merlyn for help and betray him? Is our feelings, though just, against a guy so important that we should sacrifice the whole city for it? I get it, and in their position I'd despise the idea, but I'd do it because the people would benefit from it.
Oh, Oops, I was mainly talking about the second part, with Oliver training with Merlyn. This has horrible idea written all over it. I'm on the fence about using him to kill Brick. The whole transition from season 1 to 2 was about going from a killer to a umm "wounder" I guess. Using Merlyn to kill Brick seems like a step back. I can see why they voted, but also I think it'd have been interesting if they'd used him to do it, and then have Oliver return right after. (Especially since using Merlyn to kill Brick mirrors Merlyn's history of using Thea to kill Sara and Oliver to kill Ra's (which went awesome)).
Actually storywise, that'd be a pretty cool way to go. Morally what they chose is fitting into the theme of the show.
(Still does anybody believe Merlyn's going to be all faithful teacher to Oliver through all this?)