I think it's because Tobi was really an emo boy who couldn't get over his crush and blamed the world for his emotional frailties. I like Tobi but I hate Obito.
He hasn't killed or GG somebody with kamui though. He killed three anbus covered in blood without kamuithe point of the phrase "Kamui GG" is that kamui is the most unfair single technique in the entire manga, giving its user total and utter imunity to ninjutsu, taijutsu and senjutsu, with the sharingan making them highly resistant to genjutsu. the only counters are massive amounts of explosions, countering during obito's attack, and having kamui.