The problem with this stuff is that everyone quickly forgets that this car passed every crash test with flying colors until the IIHS's most recent test, including the offset front crash where all the force is concentrated on only 25% of the front of the vehicle hitting an immovable barrier. I don't know about you, but that seems to simulate the kind of accident that is the drivers fault. That's hitting a tree or a telephone pole or a wall.
If this car was "safe" a couple of years ago before this new test, then it's safe now. The IIHS just raises it's standards periodically and adds new tests that are harder to pass, and most cars don't do as well on those tests until they make some changes. This happens time and time again. It's a good thing because we want the IIHS to drive safety forward. But it's silly to get anxious and filled with righteous indignation over it. Mazda built the 5 to pass all the crash tests out there with flying colors when it was designed, and it did. Anything you looked at a couple of years ago would have told you it was "excellent" and a safe car. It's not any less safe now, it just didn't do as well on a new test that is much more demanding, guess what, A LOT of vehicles fell short of the mark on that test. Some will be redesigned, like the CX-5, other car makers will wait until their next redesign to address it. In the case of the Mazda5, it is an extremely low volume seller for Mazda (they sold only 7,000 this year in the U.S.) and it's going to be discontinued after this model year. So, in my opinion, it's completely forgivable that Mazda doesn't go back to the drawing board and redesign the front end of this car to perform better on one test, when it already passes every other test with great scores.
It's going to be OK, I promise. The Mazda5 is still a very safe car, but cars get safer all the time. There will always be something safer, and there are plenty of cars that are LESS safe than the Mazda5 that are still sold. If you looked at cars designed 10 years ago you would have a hard time finding many that perform as well as the Mazda5 does on the all of the same tests.
Cars will continue to get safer. Mazda has done nothing wrong here. There's no scandal or conspiracy here. If you are really worried you are going get T-boned by a cement truck or drive head first into a brick wall with only 25% of the front of your car, then don't buy a Mazda 5, maybe you should get a Ford F-450, fill the door frames with concrete and hang spare tires off the sides like a tugboat.
Me? I'm OK with any car that gets high scores on all the recent crash tests except for 1 or 2 extreme ones that were just added and which many cars don't score high on. I like to be sensible about safety but I'm not going to live my life in fear.
If you are concerned about safety, I suggest you focus on improving the single most important bit of safety equipment in any car. The driver.