He's not a pedo.Rin was the closest person to him.her death is what made kakashi realize that the world was filled with hatred,pain,suffering,war,death etc and he decided to change that.
He cares for Rin,and wanted to be with her when they were both together on their team.Since then he wanted to change the world so there would he peace and noone else would suffer again,be killed lile rin,etc.