To literally love one's enemies when they continue to indulge in cruel, wicked acts is made more understandable by a passage in Mosiah 26:31. The Lord says: "And ye shall forgive one another your trespasses for verily I say unto you, he that forgiveth not his neighbor's trespasses when he says that he repents, the same hath brought himself under condemnation." I have found it much easier to pray for and forgive a wicked enemy when he at least says he is trying to repent.
However, the prophet Zenos did not wait for his enemies to repent. These enemies had persecuted Zenos and cast him bodily out of their midst. Nevertheless, he prayed for them, and in due time, many of them became his friends. As for the remainder of his enemies, he continued praying for them, but since they did not repent the Lord destroyed them. The success of Zenos in praying for his enemies is described in Alma 33:4 and 10.