That's the same problem as with all of the FBI terrorist entrapment. What if people have an honest desire to kill, but lack the intelligence, means, and/or motivation?
Do you give them ideas, pretend to give them the means, and encourage (or even nag/pressure) them? I mean, we do, but is that a good thing? Especially seeing as while we're doing it we're giving them ideas, we may accidentally give them the means (or at least an idea of how to find the means themselves), and in a time crunch to show results the pressure that we put on them to carry out the act may actually become threatening?
More applicable to this specific case, which is obviously why the guy is sensitive about it, is that people sending unsolicited requests to murder people to a site called rentahitman.com are very stupid. They're the least likely to be able to carry it out, although I acknowledge that's probably somewhat offset because they may also be too stupid to understand the probability or consequences of failing to get away with it.
The writer sees the same thing, which is why they gloss over the fact that he has put in effort to dress the site as a website where you order hitmen online, with splashes of satire to signal to people of normal intelligence and ability to detect sarcasm that it is a joke. It is never mentioned explicitly that he's dressing the site that way now until it's implicated by the discussion of the "jokes and clues to show it wasn't the real deal" halfway through the article.
Before I got to that, I thought he was a guy who had an innocent site marketing himself as a network contractor who would get sucked into the nefarious plans of stupid strangers because of his domain name. Afterwards, I decided that he's a guy who got sucked into one nefarious plan of one stupid stranger, got her busted, and loved being the center of attention and having his ego stroked by law enforcement. To get that feeling back, again and again, he turned his site into an phishing expedition for people stupid enough to think click-to-murder could be real. This is the same as Nigerian prince scams that intentionally use bad grammar and spelling to limit the replies to suckers. It's a confidence scam filtering the crowd down to the marks.
The moral hazard I see is that if you sold the site convincingly, in a way that could trick people of closer to normal intelligence, that might result in danger for you. Somebody normal tricked into prison by this might send a real hit man after you (or maybe a lawyer.) So instead, he focuses on people like the moron he started with, who don't scare him at all. If they don't scare him, are they really scary?