@fmf said
Do you think this attitude of yours is in any way a result of growing up in a culture imbued with religious values or do you think it is an unexceptional and understandable product of a more humanist outlook?
Some of both.
A common saying in my religious community was, "love the sinner, but hate the sin". While this statement is a bit too extreme on both sides, at least it gets the part about avoiding hating actual people right. Not all brands of Christianity avoid that part.
Outside of Christianity, I refined the view, with some help from Buddhist thought. I feel no obligation to love a serial killer, but it is helpful to remember not to descend into rants about how wicked the guy is, because that basically takes the suffering he has inflicted on both himself, and others, and keeps spreading it around. Far better to cut it off before it does any extra damage!
As far as "sin", I have never cared for that word, because it paints all moral wrongs with the same brush. (Some things that were considered to be "sins", I did not think were morally wrong at all. Example: man and woman sleep together 1 day before their wedding night.) Simply put, minor moral wrongs don't seem to deserve hatred, period.