Probably because he isn't as devious as you are and hasn't divined said deviousness in your invitation.
Why do you want to invite someone who broke up with you to a dinner party ?
he wants to cramp your style and make sure you remain available to him, tell your friend you dont want him there as it could spoil a good opertunity for you to meet someone else :)
its his lovely controlling side, he wants to keep you ate arms length just where he can use you he doesnt want you in a new relationship!
ohh i just realised YOU are doing the inviting!! ok scrub that your just nuts lols
its my fault too, i should have read the question more carefully before replying but then us guy's brains are not as convoluted as you girls lols
good lucj whatever happens :)