I hope it is fake and Celtic do release a statement because that'll Be funnier than Dev denying it to the hilt
Ask yourself Who is/are the fan/s who got the letter? Which Celtic fan in their right mind would advertise the fact they got sent it and why would they contact the Record about it? Why is there no name on the letter which is addressed to both "The Seat Occupier" and "Dear Supporter"? IF a whole section got the letter then who complained in the first place, someone in that section? I can't actually believe some people have been taken in by this.
Story first appeared in the Record 16 September: http://www.dailyrecord.co.uk/news/scottish-news/pongs-bhoys-celtic-write-supporters-6451555 This was in The Sun on the 15th: https://www.dreamteamfc.com/c/stockport-move-clean-smelly-fans/
It does seem a bit of a coincidence Funny though. Hope Pistol bans all these reporters who reported it