However, the two or three witnesses were not there to attest. He was faithfully upholding His Word. But the greatest of these is love. This is an exhortation by Paul to the saint of Corinth to exercise their many blessings. In no way does this contradicts God's Law to hate evil.
Love is the key to happiness.
Loving Christ with all our heart and all our soul is the key to eternal life and also happiness. We must repent of our sins, and name the name of Christ to have these blessings. The only happiness one can obtain is by loving God. And, if you love God, you will keep His commandments. We know just because you like, enjoy or even love something does not necessarily mean it is not sinful.