Why Snape is more culpable for having been loved?

[kvapost]

No: HPFGUIDX 171466

Hi all
I don't get JKR's statement that "someone had loved Snape and that fact 
made him more culpable than Riddle, who was never loved. "
What does having been loved have to do with one's culpability?

Any thoughts? Preferably not from a religious POV, just common sense.

Kvapost (who's going to get a copy of DH, open it on a random page in 
the middle, only read a couple of words as a little teaser/spoiler and 
spend next few minutes making final theories and trying to find her 
inner Seer. And then, then switch the TV, phones and internet off and 
dive right into it until she knows all the answers to our questions)