I mentioned on the other thread that my daughter has also been both biter (on "just" a couple of occasions) and bitee. From speaking to other parents, the vast majority of those who have (even short lived) biters feel mortified and do take it seriously.
In a similar-ish vein, the biggest issue I had with my daughter up until she was 3 or so was over affection, done with the best of intentions. She is a very tall girl and would, in rushing to hug and kiss another child, often either squeeze them too hard, or knock them over completely, not knowing her own strength. I appreciate that this could be a bit frightening and may result in a bump or a knock as well so obviously used to try and intervene when I saw her approaching another child, and repeatedly told her, and discussed with her, how she had to be gentle, how other children didn't always want to be hugged, how she should ask before grabbing them and so on.
Most parents whose children she knocked over were fine about it because they could clearly see that no malice was intended and, that we were apologetic, and that we would reprimand her for being too enthusiastic. The nicest ones would say "please don't worry, s/he has got an bigger brotherm, s/he's used to it". However ......... I can honestly say that I was made to feel like an absolute pariah at Tumble Tots when she 1st joined at the age of 2.5. Despite my apologies, and my obvious efforts at preventing this (but, as others have pointed out, children do move quickly, and I could hardly put her on a lead) the totally filthy and disparaging looks I used to get from some of the other mums there made me feel like an outcast and the most reprehensible mum in the world.
The point is ...... very young children do not have an innate sense of social responsibility - this has to be learnt and doesn't happen overnight. Anything which causes pain or distress to another child is basically wrong but some people appear to think that a single, or a very few, incidents are reason enough to banish and/or label the guilty child forever more, and that if parents cannot instantaneously stop them they must be irresponsible.