Rightly so. Words can't really express the lack of loyalty but, more pertinently, lack of consistency and terrible lack of PR sense from the man who has traded Villa Park for the Etihad Stadium.
And former Newcastle United striker turned BBC pundit Alan Shearer's reaction sums up one half of the ill feeling towards the ex-Aston Villa midfielder.
Indeed, Shearer, who was a Newcastle icon for the amount of goals he scored for the club but also for the amount of loyalty he showed to the Magpies, poked fun at Delph's Manchester City move.
Barton had his ups and downs at QPR but, again, showed nowhere near the disloyalty Delph has in promising to stay at Aston Villa before signing for Manchester City just days later.
Didn't Delph say he was staying?— Joseph Barton (@Joey7Barton) July 17, 2015
What a fascinating day in the transfer market. But a depressing one indeed for the Villa faithful...