We have something of a dilemma when it comes to an understanding of creepiness or disgust. Why do some people set off our sense that they're creepy? In my opinion, there's no common set of stimuli that we all respond to. No, it's more likely to be the result of individual trial-and-error learning. Furthermore, there is no "look" to people who are real creeps: you can't reliably distinguish between sex offenders and golf pros. Unfortunately, people often pride themselves as being good judges of character. Here's a heads-up, folks: People who are found to be creepy look like everyone else, unless they do some serious self-handicapping, like the villain in No Country for Old Men.
To give you an example of such self-handicapping, having facial or neck tattoos usually sends a signal, which is not complimentary unless you are trying to look fierce while in maximum security state facilities. They scream "ex-con" and "loser", very much like an above-the-buttocks tattoo screams "tramp stamp."
No, creeps are reliably known as a result of their acting creepy. The smooth-talking preacher who peeps in windows, the politician who has an underage woman in tow with him at those good government conventions, or those smarmy people on morning television do it. However, there are a number of warranted genuine creeps who fly under the radar, so to speak.
The best strategy is to let the creeps self-identify. Concoct a slogan, "I'm a creep, and I am proud!" And sell hats for them to wear. Most will be proud to do so, given their twistedness:
For the more subtle ones, a Creepometer may be of value, should someone invent this useful gadget:
And, of course, the Stare Test is foolproof. If he stares at them for more than 10 seconds, he's a creep!