Mr Everard cannot have been dismissed for starting a website with the name pccc and posting porn on it.
Posting porn on the internet is not illegal in itself and BA does not own PCCC (I hope) so why did he get dismissed?
As someone who deals with a lot of disciplinaries, you can sack anyone for anything at any time quite legally. The issue however is whether a tribunal would feel the dismissal was unfair (note NOT unlawful).
So in ME's case BA can dismiss for whatever reason they choose.