Well, one thing: why do people not have the problems with Kurama that they do with Obito? Numerous times Kurama has tried to kill Naruto out of pure hatred. And whether or not he "technically" killed Minato and Kushina, the intent was there.
I don't really have any problems with Naruto thinking Obito is a cool guy. He sees the best in people. He saw his memories of his old life, and in those memories he probably sees himself. Obito realized that he is scum for his despicable actions and deserves no better death- in fact, he was happy to go out and leave his life behind. He did what he could to make up for his actions even though nothing he could do would ever be good enough. He fought the good fight and did what he could- for that, he is cool. Spitting on his ashes for eternity isn't going to do anything. There is nothing that anyone, even he, could do that would be good enough to make up for his actions. He changed and that's what matters in the end, so forgiveness is the only way about it, lest the cycle of hatred continue.
Kurama was trying to escape his prison, a prison he didn't deserve to be in, However humans felt he was too dangerous so kept him prisoner. Neither of his previous Wardens cared much for him either so his stay inside prison was not exactly a pleasant one. You feel sorry for Kurama for the predicament he was put in, and couldn't blame him for hating humanity, he was created to protect Humanity instead he was feared and used.
He couldn't control his actions when put under Madara's Genjutsu, and then later under Obito's Genjutsu, He's technically didn't try to kill Naruto, he's tried to get Naruto to give into his hatred so he removed the seal, so he could escape his prison (a sad side effect it would kill Naruto) Kurama knows he can't kill Naruto with him sealed inside, as it would kill him as well and he would take a number of years to revive.
Obito is a different matter, he saw one person he loved die infront of him, he wasn't tortured or controlled, he lost faith in humanity too easily, out of all the villain flashbacks his was the most lame and unforgiving, even Madara saw his brothers die, grew up seeing soo many people die (not one person but multiple) he saw his clan treated as outsiders even after peace, and got manipulated by false information on the tablet. Negato saw his parents die infront of him and didn't crack, he grew up on the streets in poverty and saw constant death because he was unfortunate enough to be born between two nations at war with each other, and still didn't crack however Yahiko taking the weapon Negato was holding, and then forcing it in his heart, forcing NEgato to kill his best friend to save another is what made him crack.
Obito's flashback was depressing, to see the person who resembled Naruto the most give up so easily can't be considered anything more than trash, atleast in his death he gained some redemption, but still can't make up for the thousands that died due to the war he started.