Our Lord Jesus Christ himself showed us how this command should be put into action. Jesus wept over the refusal of the people of Jerusalem to believe his message just as they had refused to believe God's messengers the prophets in the past. Indeed they killed several of them just as they were going to do to Christ himself. Yet he loved them and prayed for them, even on the cross.
The followers of Jesus had to learn just how hard it was to love their enemies as they went out to preach the Gospel. Many of the apostles were killed. Paul suffered beatings, stoning and ultimately a cruel death. This has been a pattern throughout history. It is no different today for many of God's people. The world hates them and abuses them.
Jesus did have harsh word for those who blasphemed against God but he did not let hatred eat into his own heart. That is a very important thing to remember. Hatred destroys us if we give way to it. When people despise you for being a Christian and living in a Christian way pray for them love them in spite of what they think of you "This is the kind of life you've been invited into, the kind of life Christ lived." 1 Peter 2:21 (The Message)
Dear Lord Jesus, I confess that I find it hard to love those who despise you and despise me as your follower. Give me the grace to love and pray for them. Amen.