"Ex-girlfriend", "Ex-boyfriend". Probably some of the most despised words in the history of mankind.
Exes are routinely detested, purely on the basis that they shared *something* with your partner, once upon a time. Your partner will categorically despise your exes, too, on the same basis, yet you fail to understand why they have an issue with someone you stopped loving long, long ago (if you ever DID love them in the first place).
Allow me to embellish from a personal perspective.
I despise all of L's exes. Of course, when we first met, we were able to laugh about our past encounters without it cutting out the very crux of our souls. It didn't feel like a dagger was being stabbed into the pit of my stomach when he mentioned an ex. We even talked about how annoying it was that prospective partners hated exes, and how pathetic it truly was.
Because it IS pathetic. Why do we harbour such issues with people from our lover's past? Why can't we see them as people who effectively led them to us, taught them what they did and didn't want from a relationship, and gave us some life experience?
Would you really want your lifelong partner to be a total virgin? I personally think I'd see that as more of a threat than someone having a track record of utter whoredom. They would have no idea what they were missing, which is far more dangerous than a few memories of a failed relationship (or six).
To be fair, L's exes only ever matter to me when I have a severe case of PMT. Otherwise, I can see it from a mature, sensible perspective. I prefer to look forward than to dwell on the past. Having said that, I would wish them all dead were it not for the fact that, had he not dated them, he would no doubt be a different person than the man he is today.