I don't think Giles was mad at Buffy exactly, more concerned that she was passing her responsibilities on to him. Remember that even after Joyce died Buffy was fully able to look after and discipline Dawn whenever necessary.Giles gets mad at her for putting all of the disciplinary action for Dawn on his shoulders. I understand that is not at all what Buffy should have done, as she was supposed to be acting as the parent/guardian in Dawn's life and shouldn't have let her get away with all the klepto nonsense, but was it really a good idea for him to just leave?
Not buying it personally. This is Giles, the one person who figured out at the start of S3 that what happened in 'Becoming' was way worse than anyone thought and pushed (in a sneaky and brilliantly way) for Buffy to open up about it so she can start to heal.Whilst her 'back from the dead'- ness was a serious problem Buffy hid the extent of her trauma from Giles for no real reason (he wasn't to blame for the resurrection after all) so he perhaps didn't realize the full extent of her pain.
Maybe if Buffy had blurted out 'I kissed Spike after the musical!' then Giles would've reconsidered his departure.
Good point about Giles' intuition since he does voice the fact that no of them 'know where Buffy has been' during her dead-time.This is Giles, the one person who figured out at the start of S3 that what happened in 'Becoming' was way worse than anyone thought and pushed (in a sneaky and brilliantly way) for Buffy to open up about it so she can start to heal.
To be fair when he's not wearing tweed he does sometimes wear chunky 'Dad' sweaters a lot; especially in S7. So Giles' wardrobe doesn't help.Giles is permanently stuck in “dad” category.