In my experience the 3 little words “I’m not being … ”, (insert the relevant missing word of your choice) are often the precursor for an insult or other offensive comment.

1. “I’m not being rude, but …”. Meaning – I am going to say something insulting. I am, however going to deny my intention to be rude.
2. “With respect…”. Meaning – I have no respect for you or the ideas you are expressing. I am, however going to use those words as a figleaf to hide the fact I’m insulting you.
3. “I’m not racist but …”. Meaning – I hold highly reprehensible views on race. I am, in fact a racist bigot.
4. “Some of my best friends are …”. Meaning – I don’t like this particular group of people, however I hope to disguise this fact by using the forgoing words.
5. “Its not you, its me …”. Meaning – It is (in my opinion) entirely down to you that this relationship (insert relevant example) isn’t working. I am, however going to let you down gently by pretending that it is all my fault.

Shakespeare’s words, “One may smile and be a villain” spring to mind.