First of all, you don't have to agree with him.
But you have to know, that every personal and emotional attachment will hinder the Love and Truth of God for you to work out.
Matthew 6:14King James Version (KJV)
14 For if ye forgive men their trespasses, your heavenly Father will also forgive you:
As long you hold a grudge, you are hindering yourself to remain/abide in the Christ Body and Christ Family.
God said to Dr. Petti Wagner
Free Christian Teaching TV - The Story Of Dr Petti Wagner, USA
"The Lord impressed on me that I should forgive all those who had been responsible for my kidnapping and murder. I could not understand this. 'Why?' I said. 'If I could pray, I would be praying for myself!' God said, 'If you do not pray and forgive them right now, then it will interfere with the work you and I have to do together'. I said, 'Lord, I do not know how to pray'. He responded, 'I will teach you'. He told me to say, 'God forgive them, they knew not what they were doing'."
Nothing wrong in itself, if your daughter admires her boyfriend. That's good. Actually that's very good. The way it should be.
God loves him as he loves your daughter. His Agape Love is beyond all that.
And remember: the ideal relationship is the one that works towards Christ and his covenant in and through marriage.
Ephesians 5:22-33King James Version (KJV)
22 Wives, submit yourselves unto your own husbands, as unto the Lord.
23 For the husband is the head of the wife, even as Christ is the head of the church: and he is the saviour of the body.
24 Therefore as the church is subject unto Christ, so let the wives be to their own husbands in every thing.