I may be completely wrong here, but I think we aren't quite getting the whole story.
I agree with the consensus that you should have shared the image with the clients first before putting it on social media.
The tone of his message is rude - but having read it I think it sounds as though it is in response to a message you sent him? I am guessing you put the images up, he sent you a message to ask why you had done it and you responded saying it was your prerogative as its in the contract, your IP etc. and then he responded with the message you are showing us? I may be off the mark though.