There's plenty of reasons to not have those cloying stick-figure family stickers in your window: they're insipid, dorky, and kind of saccharine. But you know what they're not? Dangerous. Even though fear-mongering local news stations want you to think so.
These warnings have been around for a while, and they're not going away. In fact, there's been a recent surge in popularity of the warnings, which many newspapers and other news outlets are breathlessly reporting. And, really, it's all just fear-mongering.
Here's the reasoning behind the warnings: bad, bad people will look at the back window of your Nautica Edition Mercury Villager or Quest or Town and Country or whatever, see these stick figures, and know everything they need to know about you to commit horrible crimes. There's five of you in the family? Perfect. Three are kids, and two are parents. Interesting ratio. The kids have genders? Excellent. Oh, and there's a dog, too. All the ingredients for the perfect crime.
Look at this example chart an Ohio search and rescue organization put out on their Facebook page:
Now, I'm sure those folks in Ohio mean well, but this is absurd. In the example, the "dad" is in army fatigues, so the conclusion is "Dad is away a lot." You know what else a guy in army fatigues could mean? "Dad has been trained at taxpayer expense to kick my ass into custard." The "mom" in this image seems to be wearing a beret and holding a paint can, though they hesitate to add "Mom may paint my portrait" or "Mom works in oils and is influenced by the work of Josef Albers." All of this is pure, rampant, ex recto speculation. There's no actual data to support any of this crap.
They even point out the crude drawing of the dog and somehow infer it's a "Small, non-guard dog." Are there versions of these stickers that offer a more vicious looking dog?
You know how else a potential criminal might find out you have kids and what you sort of look like? By existing in the same general area as you. And that means these stickers put you in as much peril as being visible in the world does. Which is to say, not much.
You know what's interesting about these pedophiles and murderers that rely on these stickers to find their victims? They hang out at the same bar as Tooth Fairies, unicorns, dragons, and whole book clubs of Sasquatches. The bar, of course, is for things that don't fucking exist. Also, they serve Ewok meat.
A criminal using these stickers to commit a crime has, and I'm going to go out on a limb here, never fucking happened. You know how rare stranger-based child abductions are? Very rare. It's far more likely the kid will be abducted by the person who bought those stickers than a stranger.
Sure, stranger abductions do happen, and that's awful, but the idea that somehow you're putting your family at risk with these stickers is absurd. By the same logic, that Calvin peeing on the Chevy logo sticker you have on your Opel Manta (you know why) is as likely to convince a pedophile that you're a giant kid who urinates constantly, and as such is the perfect victim, since you're always distracted by your constant peeing.
As others have pointed out, the hype surrounding these stickers is the worst sort of needlessly panicked and fearful thinking. Your minivan or SUV has windows, too, and that can let hovering, invisible pedophiles totally see exactly what your kids look like so they can use their pervo-rays to teleport them to their underground sex bunkers.
This is just stupid local-news fear-baiting. Don't fall for it, or, more likely, make sure your mom doesn't fall for it. You can put any kind of insipid stickers that you want on the windows of your car, and unless it's your social security number, you're not going to make yourself any more a potential crime victim than you'd normally be.
Except for maybe a Calvin peeing on a picture of Calvin peeing. That might open up a wormhole or something.