Thomas Paine said this quote

“ Loving, of enemies is another dogma of feigned morality, and has besides no meaning. It is incumbent on man, as a moralist, that he does not revenge an injury; and it is equally as good in a political sense, for there is no end to retaliation; each retaliates on the other, and calls it justice: but to love in proportion to the injury, if it could be done, would be to offer a premium for a crime. Besides, the word enemies is too vague and general to be used in a moral maxim, which ought always to be clear and defined, like a proverb. If a man be the enemy of another from mistake and prejudice, as in the case of religious opinions, and sometimes in politics, that man is different to an enemy at heart with a criminal intention; and it is incumbent upon us, and it contributes also to our own tranquillity, that we put the best construction upon a thing that it will bear. But even this erroneous motive in him makes no motive for love on the other part; and to say that we can love voluntarily, and without a motive, is morally and physically impossible.Morality is injured by prescribing to it duties that, in the first place, are impossible to be performed, and if they could be would be productive of evil; or, as before said, be premiums for crime. The maxim of doing as we would be done unto does not include this strange doctrine of loving enemies; for no man expects to be loved himself for his crime or for his enmity.Those who preach this doctrine of loving their enemies, are in general the greatest persecutors, and they act consistently by so doing; for the doctrine is hypocritical, and it is natural that hypocrisy should act the reverse of what it preaches. For my own part, I disown the doctrine, and consider it as a feigned or fabulous morality; yet the man does not exist that can say I have persecuted him, or any man, or any set of men, either in the American Revolution, or in the French Revolution; or that I have, in any case, returned evil for evil. ”