Here's the thing - it takes a lot for me to cut off contact with someone. To reference the person I talked about, I'd put up with so much from them, even though all I recieved
was abuse for my efforts - the rest of our friendship group had cut off contact with her long before I did and encouraged me to do the same for quite a while before I eventually did.
Looking back, she didn't deserve an explanation, but I gave her one regardless. I was as warm as the circumstances allowed - I explained why I was doing it, but that I really wanted the best for her.
Afterwards, I felt awful for cutting off contact and wondered whether it was the right choice. When she sent me the horrible reply, it made me realize what I'd done was right - after I realized that, I had no problem being blunt because I realized she'd never done anything to warrant me being nice to her.
I can be a bit of a doormat, so this was a massive step for me - I promise you, under the circumstances cutting contact with people has occured, I've been much warmer than they've deserved.
Like I said, though, I know some don't agree with explaining things before you cut someone out - personally, I don't like the idea of not giving one. I mean, you're cutting off contact with someone - it's quite hard to be nice about that, explanation or no.