No I would not say anything to them, what good would it do? Its not up to them to 'redeem' themselves for your pleasure -it's up to you to either accept that which has made you dislike them or walk away. If the person asks directly why you have ostracized them, then is the time to tell them why.
I have a 'gift' of being able to sus someone out pretty quickly, someone said I was an Empath, its a double edged sword. I try to balance this by giving the person a chance, but 100% of the time I'm proved right, sometimes in spite of the fact I don't want to be proved right. This was proved recently by a girlfriend of one of our nephews., a well to do popular Lad with his own business this girl was all over him, they were apparently soul mates, lovers and best friends. He has had a run of bad luck and she's seemingly disappeared of the face of the Earth -no longer wants to know him. I knew from the start she was a gold-digger but did not say anything to anyone what would have been the point?