I believe what you are talking about there is forensic genealogy. That doesn't track down people who are in the database, but finds people who are distantly related and then, through genealogical information, figures out who the suspect could be.

In other words, the people who put their DNA up help track down dangerous criminals. This doesn't sound like something people would object to. I certainly wouldn't.

And this is not the discrimination we were talking about, unless we have now defined the tracking down of murderers and rapists as "discrimination".