It actually makes about as much sense as a psychotic mass-murderer drowning an ant-mound in their own blood, which is no sense at all, but that's the entire point of being crazy. The actions and choices of insane people don't make sense to sane people, that's just how it works. It's why they're called insane. Calling it illogical isn't an argument against it, it's just the statement of a fact. The stuff crazy people do will never make sense to people who aren't crazy. 

But at the end of the day, this is just a roleplay. Nobody actually died, and you yourself said you had a way for Ysolda to survive so nobody has to die in the RP either. On top of that, you and LeeRoy got Green's character to destroy his most powerful asset, meaning he'll be easier to beat until he gets a new one. His detonation of that mech gave you two an exploitable advantage, and all you can do is continuously point out how illogical the actions of an insane character are. 

If you can't let it go, then at least take the win, survive to fight again, and stomp him when he comes back with an intermediate-tier mech.