Not sure if you're being sarcastic or not, but pentesting is not a particularly evil activity — and you often have to look at data to see if you actually found something.

What is evil is the way that he's ensured that the predators in the dataset will never face any consequences by making the data available to HaveIBeenPwned, making it trivial for predators to protect themselves (the method through which this is possible intentionally left as an exercise for the reader), and making the data available to a news website for...some reason, but it's bound to ensure that the vulnerability will be patched out quickly and no one else will be able to access the data.

I find it much more likely that this hacker who sought out a website for uncensored AI erotica isn't actually a good guy, and might even have something to hide within the dataset. Hopefully, I'm wrong and we'll see more of this.