I may be retconning things a bit, but the more I stew on it, the more I think Gus made the right decision. He was the last thing Lorne was expecting, and so maybe the only person who could actually take him down. Everyone else who had gone up against Lorne was either law enforcement or a killer themselves, and it's always gone Lorne's way. If he had called Molly back about his hunch, seems possible (if not likely) that he could have talked or fought his way out of the situation, just like he has every time before. Gus knew Molly wouldn't kill Lorne unless Lorne was about to kill her, and Gus couldn't deal with that. "'Surrounded.' 'No, dead,'" remember? This was the only way to ensure Lorne's death, in Gus' perspective.
I'm wondering, too, how the title applies here. What bad situation is inevitable no matter which path you choose? Pepper's and Budge's deaths? (Fits with my theory, at least--Lorne was going to kill them one way or another.) I think it might actually be referring to Lester's death, though. Eventually he was in so deep and hurt so many people that no matter what he chose to do, he wasn't going to make it out alive.
