2. Diplomatic, politic, tactful imply ability to avoid offending others or hurting their feelings, especially in situations where this ability is important. Diplomatic suggests a smoothness and skill in handling others, usually in such a way as to attain one's own ends and yet avoid any unpleasantness or opposition: By diplomatic conduct he avoided antagonizing anyone. Politic emphasizes expediency or prudence in looking out for one's own interests, thus knowing how to treat people of different types and on different occasions: a truth which it is not politic to insist on. Tactful suggests a nice touch in the handling of delicate matters or situations, and, unlike the other two, often suggests a sincere desire not to hurt the feelings of others: a tactful way of correcting someone.

Did you mean undiplomatic?