1) Goat and Nefario talk in private.
2) Goat claims Nefario is holding his bitcoins hostage.
3) Nefario publicly claims that all he needs is a withdrawal address and he'll pay Goat back.
4) Goat publicly says to Nefario/GLBSE that if all he needs is a deposit address, here is one. Now pay me.
5) You claim this is evidence Goat was lying back at 2.
If Goat was telling the truth back at 2, isn't what he did in 4 exactly what you would expect -- calling Nefario's on his claim?
It is, by the way, entirely possible that Goat and Nefario simply came back from the discussions at the beginning with different impressions. Goat may genuinely have believed Nefario expected concessions for him to get the undisputed coins back and Nefario genuinely believed he had simply asked Goat to direct him how to repay him. Everything I've seen after that is consistent with this, and we do know that communications broke down at least to some extent.