What would make itachi think its a good idea to kill his whole entire family except his little brother, and then just leave him to a life of pain and expect him to grow up normally? I mean, of course plot no jutsu is the reason why he is alive but, honestly, Itachi set Sasuke up for a path of destruction. Telling his bother that he would have to kill his best friend to get stronger, calling him worthless, that sounds like true brotherly love if you ask me.