There have been, and always will be, some posters who enjoy attacking newbies.
My very first post on FT, in July 2003, was met by very nice welcomes from a number of posters and, almost inevitably, by one very snarky response.
The snark was immediately jumped on by several other posters, and I had a bit of fun laughing at him in a subsequent post, and he suddenly disappeared. He made his final post on FT 2 days later. He apparently enjoyed snark but only when he was the one posting it.
None of the responses he received (including my own) violated the TOS, hence there was no moderation action taken against him, but when he became the target he was not very happy.
Perhaps that is the best (and only) way to deal with those who love attacking newbies -- give them a taste of their own medicine.