For me there is no comparison between a loving human to human relationship and a loving animal to human relationship in regards to quality, capability, love, emotional intimacy etc... The relevance of the comparison was only in terms of the logic used to justify the relationship Biblically.

A homosexual relationship may be completely loving and wonderful and full of virtue, I don't believe this is in question at all.
The question is holiness.
Is the relationship within God's allowed bounds?

A married man may have a mistress. His wife may know of it and approve. The man may love both his wife and his mistress very much. The respective relationships may be full of virtue and good fruits. However, biblically it would be considered adultery and unholy.
The same may be true of a young (lets say teen) boyfriend/girlfriend relationship. The two may love each other very much, but still live at home with their respective parents. They may be committed to and faithful to each other. They may even be planning to 'one day' marry. But if the relationship is sexual then it's fornication and unholy.
In the papers here today it was reported that a man has a sexual relationship with his 30 yo daughter. They were both in love, happy and even had a healthy child together. Biblically this relationship is (whilst loving and wonderful to the couple themselves) unholy and therefore prohibited.
Biblically, even heterosexual marriage had/has boundaries. In Ezra 10 Israel was disciplined because they had taken foreign wives and had children to them against the holy limits placed by God. They were commanded to "Separate from them" (vs 11). Likewise in the NT widows wishing to remarry are commanded to limit themselves to Christian husbands.(1 Cor 7:39). If a Christian widow disobeyed this command would she have a legitimate marriage? Of course! Would it compromise her salvation? No! We are saved by grace. Would it be holy? NO!

Whilst love is certainly the chief goal of the law and the great teaching of Scripture, that love always has to be holy to get God's approval. Holy sexual relationships are clearly defined in Scripture and homosexual ones are simply not included.

Whilst I believe this passionately, I do not have a Biblical answer for what someone living with a homosexual orientation is expected to do... and I can completely understand why those in loving homosexual relationships feel a strong desire to 'justify' their relationships Biblically. However, since this is impossible to do they are left to either:
Focus on the love aspects which are undeniably approved of in Scripture and ignore the lack of holiness issue.
or
Say, well Scripture's sanctions are some how not relevant to us today.

So it is with deep compassion and empathy to the struggle that I have to say beware brothers for Scripture clearly says: "Make every effort to live in peace with all men and to be holy; without holiness no one will see the Lord." Hebrews 12:14.

Blessings
Cat.