flashback

Today I bumped into a person with whom I used to work many years ago but whom I haven’t seen for a long time. And out of some weird duty I was friendly to him, asking how he was and how the Christmas has been. Afterwards I realized that last time I have heard of this person was maybe one and half years ago when he emailed me shouting (in capital letters) that I should quit my job because I cannot take responsibility.
So why exactly was I nice to him?