I disagree. A friend of mine has a rishta proposal from a guy she was excited about, because he was smart, from a good family, was educated, very well spoken, and had a good job. He seemed perfect.
I also knew the guy and had personally seen him get very abusively drunk. My friends also knew him and knew that he had a drug habit.
Given the level of excitement that my friend had about the guy, me simply keeping quiet probably wouldn't have helped ward her off.
Sometimes, full disclosure of what you know is best.
I still stand by my original position - but I'll willing to concede your point.
My experiences have been with families asking about girls whose character while not sterling, was not what the rishta family wanted - so in my own personal circumstance, my using a soft approach was appropriate for the reasons I stated.
In the example you gave, I think that keeping silent about a character reference for someone who is that awaara or bad-kirdaar and who enjoys naik-naami for no reason is wrong and the person should be exposed. So maybe the answer at the end of the day is it depends on the circumstances. I wouldn't be too quick to expose all the bad deeds of someone at the drop of a hat - but I do see the merits of full disclosure in some cases.