"people with nothing to hide wouldn't be so opposed to them"

I read the title in an article about Polygraph machines or 'lie detectors' and it reminded me of similar things I had read about ID cards, routine DNA testing and just about everything else that a government churns out for 'our security'. The problem is that the phrase is so common, most people won't notice that the logic is very much flawed.
The logic to the statement is based on the assumption that the piece of equipment or system is 100% foolproof. If indeed a lie detector was 100% accurate then surely only a liar would be concerned with taking one (ignoring people who might *have* to tell lies like security services or government officials protecting the public). Of course the problem is that none of these things are foolproof.
Take a lie-detector for example. Suppose you were interviewed in a murder investigation and failed a lie-detector test. The information was then presented in a Court alongside other circumstantial or inconclusive evidence. You might very well be found guilty. Take ID cards, there could be any one of a number of technical errors that might make your card read as a fake or that would enable someone to copy it and make it look you were somewhere else to where you actually were etc. Imagine the DNA information from your routine test is mis-entered or polluted into the system and 'your' DNA is then found at a crime scene. Can you imagine getting out of that by accusing the system of a defect somewhere?
Quite honestly the original statement is nonsense and I for one will ensure I do not agree to any of these man-made systems that somehow promise our security at the expense of liberty, annonymity, money and security.