'Hate the sin, love the sinner.'

It's a phrase cited as Christian scripture. Many must think it is scripture. It isn't.

Criticism of this phrase are widespread.

It's from St. Augustine, who says in a letter, Cum dilectione hominum et odio vitiorum, or, "With love for mankind and hatred of sins."

But the Protestant reader must find it easy to believe. The NIV translation of Romans 12:9 has: "Love must be sincere. Hate what is evil; cling to what is good."

An evangelical commentator notes:
We don’t much like that word, “hate.” But it is a perfectly legitimate affection and should be cultivated by every sincere follower of Jesus Christ. 
Earlier translations of Rom. 12:9 had 'abhor' or 'detest', but 'hatred' was taken to be the point. So a theology of hatred, essentially, with Christians instructed to hate, was born. Note the Dictionary of Bible Imagery:
While people apart from God often fail to perceive his judgments, redeemed humanity can learn to abhor – and thereby turn away from – those things God loathes (cf. Ps. 31:6; 97:10; 119:104; Amos 5:15; Rom 12:9).
The problems with "hate the sin, love the sinner" are often discussed.

Here again, Old Testament law is imported into New Testament theology.

The word in Rom. 12:9 translated as 'hate' is apostygountes and is used only this once in the New Testament. Previously it became 'abhor' or 'detest', but the NIV escalated to 'hate'.

Christians were ready.

"that is, hating it, and hating it exceedingly" (M.F. Sadler)

Vines Expository Dictionary says it means 'to shudder' or 'hate'.

Dictionary of Bible Imagery:

John Piper:
Notice Paul’s verbs: “Abhor (apostungountes) what is evil; hold fast (kollömenoi) to what is good.” He did not say “Choose against evil and choose good.” His words are very strong. “Abhor” is a good translation. “Loathe,: “Be disgusted with” (Liddell and Scott Lexicon) would also be correct. “Hold fast to what is good” means embrace it. Love it. The word is used for sexual union in 1 Corinthians 6:16.

The word Paul uses in Rom. 12:9 is the only usage in the New Testament. There is no 'Paul Dictionary' and various scholars will define it differently, because they are just reading for context. Most likely, it seems to me, the idea is 'avoiding. Avoid what is evil.

The next step after all, is 'cling to what is good'. Clinging and avoiding are opposite movements.

It certainly doesn't mean a hardened stance of "hating." What is the context? It's a speech on how to love!
Love must be sincere. Hate what is evil; cling to what is good. Be devoted to one another in love. Honor one another above yourselves. Never be lacking in zeal, but keep your spiritual fervor, serving the Lord. Be joyful in hope, patient in affliction, faithful in prayer. Share with the Lord’s people who are in need. Practice hospitality. Bless those who persecute you; bless and do not curse. Rejoice with those who rejoice; mourn with those who mourn. Live in harmony with one another. Do not be proud, but be willing to associate with people of low position. Do not be conceited. (Rom. 12:9-16)
Far from 'hating' the sinner, the passage instructs to 'bless' people acting very badly and be willing to 'associate' with just about anybody. "Do not be conceited" means you aren't any better!

It's God who's better and He wants us to love.

Intro to Christian Teachings on Sexuality: "Be as the lilies . . ."

When Jesus tells us how to be, he uses the image of a lily.
Consider how the wild flowers grow. They do not labor or spin. Yet I tell you, not even Solomon in all his splendor was dressed like one of these.

Growing up Christian, I never understood a basic fact about scripture.

In all biblical narrative, God makes 'covenants'- or contracts- with believing humans. The Christian covenant is defined in John 13:34, when Jesus says: “Love one another.”

There are no further ‘rules’.