Due process of law means merely that -- the government cannot deprive you of life, liberty, or property except in accordance with the law. Different Constitutional provisions address which types of laws can be enacted, and which types of laws cannot be enacted.
To put this entire issue in perspective, contrast the potential abuses of DNA databases (if any) with a real life example of gross abuses of our freedom: the pervasive (and pernicious) use of progressive taxation to redistribute wealth in this country from those who earn it to those who don't -- "from each according to their ability, to each according to their needs," not in a Communist country, but right here in the USA. From my perspective, obsessing about potential abuses of DNA databases doesn't even rise to the level of focusing on the gnat on the elephant's butt.
Yes, so they are changing the law to make this obscenity part of due process. That is the problem. There is this pesky little thing called rights that the constitution is supposed to protect. It gets in the way of the government aims - so we pass a law and 'voila!' ignoring that pesky little thing is now part of 'due process'.
Yes, our tax situation is beyond terrible. While I want them to leave my money alone, this is getting into the my life and my body area - that can't be replaced -