I don’t know how many of you remember but a few months ago (forsure no more than 4) a couple of guys were arrested, they were going to blow up shuls in Queens and I think Riverdale. Their plan was to dress up as frum Jews and walk right in. Thank G-d they were caught before a tragedy happened. Maybe we didn’t really learn the lesson then, that we have to be wary or strangers no matter what they dress like. Or that just because someone dresses differently than us doesn’t make them a bad person (whether morally or hashkafically ). Therefore, we got a stronger message, in the form of Levi Aron.
Just because someone looks like a frum Jew, and yes probably 99% of the time they are a frum Jew and there is nothing to be worried about, looks can be deceiving. Bottom of the line is that YOU HAVE TO BE CAREFUL. Yes, you can’t live your life paranoid BUT you have can’t be just because he looks like he’s a good person, therefore he is a good person.
It’s not only about leaving your 5 year-old with a stranger for a few minutes, that’s just an example. It’s about having the right sense to know that not everyone can be trusted.