That's another way of saying it. I've learned that the so called "safe" products have security holes as well, but since they aren't as widespread as Adobe's, no one cares. Not the users nor the hackers... If the same amount of hacking hours were spent trying to find flaws in the "safe" products I bet they wouldn't be safe any more.
I'm not against using these safer alternatives. Some of them actually work better than their mainstream equivalents, like Foxit vs. Adobe Reader. My point is that "safety" doesn't necessarily mean "flawless", only "less scrutinized".
Take MrRipleys's advice.