As we are starting to see, terrorist groups are storing as much data as they can.
If the UK authorities do not keep up with the terrorists in terms of data storage, then ...
... the terrorists will gain an advantage, and
... innocent people WILL die.
It's a pretty stark choice ... Let the authorities collect LOTS ( and I mean LOTS) of data on EVERYBODY ... or risk being killed.
And sure, they shouldn't hold data on "innocent" people.
But, if they knew who was innocent and who was not, there would be no more crimes. We are ALL innocent until we do something that makes us not innocent. And, by then, it's too late ... the bodies are already being counted.
If the security services think they can keep a better eye on the baddies by having a comprehensive fingerprint and DNA database, I will turn up at the station tomorrow to give my samples.