Wrong! His group was fighting for Serbian Nationalism. Serbians are Orthodox Christians. His personal belief was atheism, but so what, the cause was Serbian Nationalism and it was a broad based movement, just waiting for some event to set it off.
Marcelino, it seems you're awfully defensive, and it causes you to say stupid and false things.
I have a digital copy of the whole trial transcript, where it's stated quite clearly (by the assassins themselves) that they had a strong aversion to the Archduke for being Catholic.
First of all, they supported the idea of a unification of South Slavs. Not just Serbian Nationalism. Serbia was to be the "South Slav Piedmont"