The Lord never promised that the Christian life would be easy! If we are commanded to love our enemies, the presumption is that we shall have enemies. We must expect persecution if we are expected to pray for our persecutors.
This sermon was to His disciples, not to the multitude (see Matthew 5:1), and the Lord is assuming they would inevitably have enemies, just as He did. "If the world hate you, ye know that it hated me before it hated you. . . . If they have persecuted me, they will also persecute you" (John 15:18, 20).
He had even called such persecution a blessing. "Blessed are they which are persecuted for righteousness' sake" (Matthew 5:10). However, we need to be sure that any such persecution comes "for righteousness' sake"--not for any other reason than for upholding, proclaiming, and living the truth as set forth in the Word of God. "If ye be reproached for the name of Christ, happy are ye. . . . But let none of you suffer as a murderer, or as a thief, or as an evildoer, or as a busybody in other men's matters. Yet if any man suffer as a Christian, let him not be ashamed; but let him glorify God on this behalf" (1 Peter 4:14-16).
We can really love our enemies only as we follow Christ's example. "Christ also suffered for us, leaving us an example, that ye should follow his steps: . . . Who, when he was reviled, reviled not again; when he suffered, he threatened not; but committed himself to him that judgeth righteously" (1 Peter 2:21, 23). "Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head. Be not overcome of evil, but overcome evil with good" (Romans 12:20-21). HMM