Hi Amergin. I don't know what information you and the other people who are naming GUEST #1 have access to, so there's no way for me to know for sure whether or not you and they are right.
However, it has happened around here that people have publicised the screen names of people they thought were posting as various guests, and then in some cases they turned out to be wrong.
I hope you understand all of the potential ramifications of what you're doing. Not only for you, but also for the person you are accusing, if it should happen that you are wrong.
Take care,
Carol