Dingbat,
You imply that the fraud investigation was halted because of the seat being 'blocked'. Galley FM's version? Or was it halted because it had been stated several times that upgrading on board the aircraft for no reward wasn't fraud? Some wanted to get back at pilots by claiming fraud for upgrading, but the problem was, some cabin crew decided to drop their own colleagues in it too, when they saw what their forumite friends considered fraud.
As for suspending both parties, if you were the subject of a prolonged foul-mouthed verbal attack because of the position you took regarding IA, would you expect to be suspended too?
Remember this is a disciplinary procedure signed up to by Unite, and doesn't allow such a provision, nor does natural justice.