grief porn! i think that is possibly princess diana syndrome, but this is not what the OP describing here.
As other posters have said, its Empathy.
I have recently learnt of the death of a local shopkeeper, such a lovely lovely lady and it was a tragic accident. I was surprised at the extent of my feelings about it to be honest, i didnt cry because im hard as nails but i was stunned and shocked and it affected me for the rest of hte day, and i only knew the women from the shop, but it was just i think, empathy for her and her family.
I also think that this sort of thing is easy to experss than our own greif.
When my dog died, i was inconsolable, literally hysterical, it was pants as i had decided to have him put to sleep so lots of emotion, but raw and out there. Easy to get it out and deal with it.
My father died about two years later, i still haven't shed a tear - i promise you, i loved my dad more than my dog! I can't explain it. People must have thought i was a bitch at the funeral, i was like, ok, thats that then, shall we go! I could hear people crying behind me, i certainly didn't think they were encroaching on my grief.
OP, don't feel bad - its good you can express your feelings, so long as you wasnt wailing and beating your chest i dont think you would haveoffended anyone!