You never knew he was part of the Senju? That's why Obito and others say history repeats itself again, Starting with the Sage's sons who were the first Uchiha and Senju, and later on guys like Hashirama/Tobirama vs Madara/Izuna. This generations top descendants are Naruto and Sasuke and it was almost fate that they wound up as enemies for a time. I guess it was fairly easy to miss the part about Naruto. It was a short segment a few years back. To answer the other question about Obito, yes he is a bad guy. He's responsible for the second Kyubi attack on Konoha, Minato and Kushina's deaths, Neji and Konan's deaths, co-creator of Akatsuki along with Pain and is the true leader, various other random shinobi deaths, intended to kill Naruto, killed and controlled the 3rd Mizukage as well as 5 of the other 8 Jinchuuriki left, started the 4th Great Ninja War, revived the strongest creature alive and wrecked havok, removed the chakra from most of the shinobi still alive, and intends to put every being on earth under his illusion. How is he not a bad guy?