A government could gather a wide variety of data on their citizens and residents. To name three, pictures, fingerprints, and genetic profiles.
- Quite a lot of countries which are generally considered reasonably free and democratic require all citizens to have a photo ID.
- In recent years, fingerprints have become necessary for many passports.
- As you point out, genetic profiles are not yet in widespread use.
One could well argue that the three examples are just a difference in degree, not a difference in principle. If it is legitimate for a government to require photo ID, then it is just more of the same if they require genetic profiles.
But I see a few differences:
- Photos, especially without CCTV abd automatic matching, are mostly useful to verify the identity of somebody in front of the police officer or other government employee. Fingerprints and even more DNA are something we leave where we go. So Fingerprints and DNA allow a much more intrusive surveillance.
- DNA is not just an identifier, it also contains data about the individual. While the data in a DNA profile database is not useful to tell if someone is prone to heart attacks, or likely to get some kinds of cancer. Who knows what else can be predicted from DNA in the future? Once the DNA profile process is in place, testing for that would be a simple upgrade of the hard- and software.
What it comes down in my judgement could be characterized as "need to know." I accept that the government needs a picture and a signature from me so they can issue me an ID card that cannot simply be used by a thief who gets his hands on it. I do not accept that the government needs to be able to tell where I have been unless they have gone through a legal process with probable cause for a specific accusation before they can test a generic sample from me.
There has to be a balance between freedom and security. As the famous proverb goes, those who abandon freedom for security will have neither. But without some security, freedom's just another word for nothing left to lose.
Regarding implementation, it was in an era before DNA profiling, but the secret police of East Germany collected smell samples so they could use tracking dogs. They didn't do it on everyone for logistical reasons.