We enter into the resentment even of an odious person, when he is injured by those to whom he has given no provocation.
 Adam Smith, The Theory of Moral Sentiments (1759). copy citation

Context

“It is to be observed, however, that this concern does not necessarily include in it any degree of those exquisite sentiments which are commonly called love, esteem, and affection, and by which we distinguish our particular friends and acquaintance. The concern which is requisite for this, is no more than the general fellow-feeling which we have with every man merely because he is our fellow-creature. We enter into the resentment even of an odious person, when he is injured by those to whom he has given no provocation. Our disapprobation of his ordinary character and conduct does not in this case altogether prevent our fellow-feeling with his natural indignation; though with those who are not either extremely candid, or who have not been accustomed to correct and regulate their natural sentiments by general rules, it is very apt to damp it.” source