General Rudeness:
* As blunt as a brick.
* As abrasive as sandpaper.
* As sharp as a tack.
* As crude as a barn door.
Disrespectful:
* As disrespectful as a dog with a bone.
* As inconsiderate as a runaway train.
Offensive:
* As offensive as a rotten egg.
* As hurtful as a poisoned arrow.
Arrogant:
* As arrogant as a peacock.
* As haughty as a queen.
Insensitive:
* As insensitive as a rock.
* As clueless as a baby bird.
Remember to choose the simile that best fits the context and the specific kind of rudeness you're trying to describe.