Answer:
Thucydides attitude towards the Peloponnesian War seems pretty clear: it caused a lot of suffering and hardship for people on both sides of the fight.
As for his attitude toward Athens, this is a bit more difficult to pin down because Thucydides' fellow Athenians had exiled him from his native land for 20 years because he had failed to bring reinforcements quickly enough to the Athenian forces at Amphipolis in 423 BCE. Thus, it is difficult to imagine that Thucydides would have had any great love for the people who exiled him for 20 years.
It was also my fate to be an exile from my country for twenty years after my command at Amphipolis; and being present with both parties, and more especially with the Peloponnesians by reason of my exile, I had leisure to observe affairs somewhat particularly. I will accordingly now relate the differences that arose after the ten years' war, the breach of the treaty, and the hostilities that followed.
