Well, the reality is that the vast majority of gun laws in this country aren't normally enforced - for precisely this reason.
For example, if they started taking lots of average gun owners to court for having folding telestocks on their AR-15s, the vast majority of judges and juries would see the idiocy (come on, a fixed and folding telestock are nearly the same thing, even to a complete gun neophyte) and before long, there goes the AW "evil features" bans.
For this reason these laws are RARELY enforced, and when they are, it's to add charges to somebody who's already in a whole lot of trouble for more serious crimes (drug dealers, murderers), and even then in many cases the firearms charges are eventually dropped.
Things like the "evil features" ban and the high cap ban don't exist because they think gun owners are criminals - they exist because they (meaning ATF and other involved agencies) know that legitimate gun owners are SO honest and law abiding that these rules will end up being self-policed.
Look at all the condemnation anyone who suggests putting a pre-ban upper on a post-ban lower will get on AR15.com. Many people here (who don't possess preban guns) wouldn't even allow a pre-ban upper into their homes out of fear of violating the law. Yet (and I'm not advocating either way) please name for me the hundreds of people you know who are rotting in jail or even just had their firearms confiscated for the *sole reason* that they did something like that. Pretty hard to do.
In other countries (Australia and England come to mind), gun owners' honesty was used to take their guns away. I'm not saying we should all start putting together full auto CAR-15s on post-ban receivers, which probably WOULD have the result of a big list of people sitting in jail. But it's just something to think about. We are our own worst enemy in many ways.
Personally when I see a violation of many of the more clearly unenforceable firearms laws, I ignore it. It is not my duty to play ATF (and local and state LEOs - it is not your duty either when the law is in violation of the constitution) and I have no desire to follow in the footsteps of the Nazis, who ratted on their friends and parents.