User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4405022-20130224224515/@comment-3146930-20130303213858

Because before the two camps weren't fighting each other. During The Mark of Athena, full out war broke out between the Greek and Roman demigods, leading the gods to become split as both of their personality's want to help, they just can't decide which side to help. It is the reason the other gods were so mad at Hera/Juno, as she was the one that tried to get both camps together which in the past has lead to fighting, including the American Civil War.

As far as Athena's statue goes, the reason Athena/Minerva is so angry is because the Roman's took Athena's statue when they attacked Athens. Then when the Romans adopted the Greek gods, the Romans had war gods of their own and stripped Athena of her importance as a war goddess, leading Minerva to become resentful as is her Roman form, she was only a goddess of wisdom and crafts while she used to be so much more. At least that is how it is explained in the book.