why is it we always seem to do exactly the opposite of what we say?

• "I don't mean to offend you"........I am going to offend you now
  
• "I don't mean to be rude"........I am going to be rude, but I want to feel okay about it
  
• "I don't mean..."........

how about we stop prefacing these things we are saying and we just say them. prefacing doesn't ease the hurt we are about to experience

but somehow if we don't preface we are jerks...am I supposed to acknowledge the pain I am about to inflict before every thing I do or say?