There are certain phrases that sound like you are being very respectful when, in all actuality, they are very rude and meant to be insulting. You know which ones they are because you have used them on a number of occasions. I don’t know who the first person was who coined the phrase “no offense,” but he/she was a jerk. In essence, when you premise a statement by saying “no offense,” you are preparing that person to be insulted right then and there.