Everybody, or rather many of us have a past that may not be of such a beauty, something that is not to be proud of. Nonetheless, judging a person from his past may not be an entirely fair proposition, given of his circumtances and other unknown factors at that time, that may have led to him to be that way.
Why not we start accepting those around us, from the potential that is ingrained within themselves. They have the capacity to become better people, in ways that perhaps now we could not really imagine.
Everyone has the means to change, and transform into a greater persona. Some can do it by themselves, some others need a little bit of help, from us.
May Allah help all of us, Insya Allah.