Why do you think tact is an important quality?

Tact is important because communication is not only about simply saying what you want to say but having it heard, understood, and absorbed by your audience.  If you are rude and offensive your audience will just tune you out or even leave and your message will go unheard.  Through tact, you can communicate your message, even if it is a difficult topic, and have a better chance that you will actually be heard on the other side.

Hope that helps.