I think it was necessary.
Part of attracting players is the clubs reputation on how you'll be treated if you sign. From the outside we look like decent employers who will look after you if you've got a long injury, give older players career routes into badges / coaching etc. This all factors into which club players choose to sign for and if he's damaging that reputation by being conservative with the truth then it should be put right.
Also, he's the one that chose to put his own contract negotiations into the public domain so I think the club were free to respond. Aye, it's not our usual style, but I wouldn't say it's particularly emotive or unprofessional. Out of the 20-odd paragraphs there's one line "we are disheartened".... the rest is more or less a statement of fact.