It is not simply a matter of saying it endangers none but criminals (even if we ignore the possibility of planting DNA evidence or false positives.) Criminals still have rights; all the same rights as everyone else until/unless convicted. If police knock down every door in a neighborhood looking for a kidnapper, finding him behind one no more justifies knocking down that door than any of the others unless they had probable cause to suspect he was there, or a warrant to search the premises (which they cannot get without the aforementioned probable cause.) Likewise, if they get a warrant to search for stolen money and instead find a murdered hooker, that is poison fruit and inadmissable; a warrant is not a fishing trip, and an arrest certainly should not be.

At most, arrest grants (or rather, REQUIRES) probable cause to suspect commission of the SPECIFIC crime for which a person is arrested, or, in the parlance of the Fourth Amendment, "particularly describing the place to be searched, and the persons or things to be seized." Arresting someone for a simple assault, collecting their DNA and using it to convict them of an unrelated rape and murder after they are cleared of the assault is abuse of power. It is also precisely what happened here. Arresting someone for, say, driving drunk when stone sober, collecting their DNA and using it to convict them of murder is improper because 1) they had been proven guilty of nothing (and were thus entitled to presumption of innocence) and 2) there was no probable cause to suspect them of the specific crime they DID commit (only the one of which they are innocent.)

Unless DNA is collected as evidence of a crime of which they are already suspected AND subsequently convicted, or they are convicted of a crime WITHOUT the DNA as evidence, I cannot see how it is anything but poison fruit, just like if cops dug a murder weapon from under someones bed when investigating a false claim of drug possession.