Totally agree with this summation of Javert's character. He's not a bad man, but he just doesn't see shades of grey in people. Either criminal or honest - no inbetween.
The way the show is done is in such a way so that you only hate him for the first portion of the story. By the time he sings "Stars," you are encouraged to start to understand him and empathise a little more with him. His song is one that should make you feel that way, and the words explain where he is coming from.
I've not read the book though, & the show doesn't really explain his particular raging need to capture Valjean, who after all, only broke parole, and his crime before that wasn't major. This just goes to show how obsessive he is about catching anyone that falls outside the law.
Another reason to love the show though. Even the bad guy isn't really a bad guy, and by the end, you are as sorry about his death as you are about, well, everyone else's.