Deleting posts, threads and banning posters leads to confusion, and leads to 'Whatever happened to the xxx thread?'
It happened to me when XV179 Crew Tactics discussion got a bit too deep.
Just a suggestion.
Pop, why don't you
quote the defendant
(so that the offence remains visible) and he can't delete it.
Then make your statement about unacceptability, but offer the defendant the chance to apologise and/or give him a week in the Sin Bin (which you apparently do sometimes)
That's what grown ups would do. Apologise for the indiscretion and move on.