Hi,
Someone does something foolish or inconsiderate or downright nasty; someone affected by this action, hits the first someone. Is the second someone still wrong, given the provocation?
If there were a general answer to this question, the whole population of lawyers would be out of a job. Can you imagine such a world?
On a more serious note: whether we like it or not, ethics has always been dependent on time and place. Without some consensus of a local majority, there is no "right" or "wrong". Even then, law is made to facilitate living together, not to do away with individuals' moral dilemmas.