I think the concern here is that Gannon was a prostitute. Which is against the law. Which should (regardless of his political views) disqualify him to be asking questions of the president and the press secretary. For two years.
Since he wasn't arrested or booked for prostitution, and the website apparently used some fictitious name, I'm a little fuzzy on how the Secret Service should have known about it.
For that matter, I'm a little fuzzy on how the liberal bloggers ferreted out the website. Do you have any info on that?