There's a case against globally accessible DNA databases from the point of view of dragnet approaches picking up people whose connection to the crime scene is either totally incidental or actually nonexistent and purely down to data mixups, but that's a largely separate issue from authoritarian police trying to massage the evidence in a case against a particular person.

If you're already a "convenient suspect" the police wish to build a case against, they don't need to find you on a consumer genetics database to be able to obtain a sample of your DNA or strongly hint that they expect to be able to use DNA evidence (truthfully or otherwise) to send you away for a very long time if you're not willing to consider moving to plea bargaining territory.