Absolutely not! It would have had greater effect if it read:
Your boss hasn't given you any substantive reason, in saying this. You should definitely ask for more details (we can't possibly give an answer with just this), and if it is a consistent and serious problem it might be better for you professionally to seek employment elsewhere. You could also just let it go.
The cumulative effect of the comment as quoted by Iain is such that it has no redeeming merit and the flag should have been accepted; it is not a constructive or professional comment even in our profession.