When I insult you
I don't swear much. I have, in recent years, taken to using the word 'fuck' a fair bit, but that is mostly because the word lends itself to such an extraordinarily wide range of uses. It is a habit that will very likely surprise people who have not spoken to me in a few years.
As far as insulting goes, I prefer to be clever and tongue-in-cheek about it. So that rules out calling people names or putting labels on them that might imply they have sexual relations with family members (who I naturally have nothing against). I don't say bastard — it doesn't seem like there is anything inherently shameful about being a bastard. It is an aspect of one's being that would seem to be entirely out of one's hands.
The worst possible thing I might ever say to someone I have a catastrophic disagreement would be “fucking idiot”. It's mostly just “idiot” with a pinch of “fucking” thrown in for emphasis and flavour. I use this insult because I do think there is something contemptible about being ignorant and stupid, especially when it is wilful.
I suspect also, that another reason I use it is because it is my greatest insecurity — being an idiot. I am mortally afraid of being stupid or ignorant. I have made it the mission in my life to know as much as possible. I read, learn, and try to constantly better myself. It seems lofty and inspiring until you realise that all of it is simply me running away from my greatest insecurity — the pit I dread falling into. The idiot pit.
The worst names we call other people come from what we suspect ourselves to be. Anger is when I take my worst self and project it at the object of my anger.