What is your take on using genealogical dna tests to solve cold case files?

I have had my DNA tested to help trace my family tree.
My brother has refused to participate, claiming that the government would create a database to solve cold cases, which looks exactly like what has happened.
News reports now say law enforcement agencies are using cold case DNA evidence to narrow suspects.
(Genealogy websites such as Ancestry.com and 23andMe had millions more profiles, but unlike them, GEDmatch had no policy against searches by law enforcement.)

How do you feel about the government utilizing DNA databases to solve cold cases?
Would you still use this kind of test for family tree research?
Does the importance of solving cold cases outweigh the implied privacy agreement?