I think that doing everything in your power to bring back your mother is a bit more justifiable than Obito's. I mean, I can get that sort of connection a bit better.
Obito's is just complete shit. Hell, he knew the truth behind Rin's death (well, not the Madara manipulation bit). She clearly did what she did for the sake of the village and her friends. Solution? Destroy the village and kill her friends. Yes, Obito, Rin would be so proud.
Not to mention that he was only like 13. Isn't that a bit early for true love and righteous vengeance? I would have bought this more if he made a slow descent into psychopathy, but he didn't. One moment to another, the guy who refused to even consider making a sacrifice for the "greater good" decided that mass murdering was acceptable.
Sasuke changing his mind... Eh, I'm on the fence. I reckon that if Kishi said that he's confused, and because of that he will fight alongside Naruto, so that he can sort himself out later, after the war, that would be believable. His respect for Itachi makes sense, and was well characterised. Him not wanting Infinite Tsukuyomi also makes sense. So this course of action would make sense:
"Hashirama, I don't know what to think, but I know that unless I help out, I won't be able to make a decision as to my position, so I'll help the Shinobi Alliance."