No. This is what people on the Autism spectrum do. Smiling Monsters are social savvy, understand body language, skilled emotional manipulators, comfortable with confrontation, and very good at slipping past people’s radar, even those trained to spot this sort of thing.
But what’s worse is you’ve just moved from endorsing action based on actual harm being done to action based on suspicion. There’s a reason “they seemed so normal” is a thing when it comes to asking about the neighborhood serial killer. Most people are horrible readers, and action on suspicions alone is more likely to harm those that have done nothing wrong than stop a sexual predator.