Why do you assume I wouldn't love my child?
I'm not at all accusing you of not loving your hypothetical child. I'm simply pointing out that by being so intolerant of their lifestyle (getting pissed when they bring their partner around) you're making life a lot, lot harder for them than it needs to be.
Love does not mean always agreeing with everything someone does. It is in many cases the exact opposite: still honestly hoping the best for someone when you are distinctly not in agreement. Loving one's enemies does not mean they are no longer enemies.
In the case of a child, I would have made a promise before God to raise that child in the practice of faith upon baptism and engaging in a homosexual act or entering into a homosexual relationship is a grave sin thus contrary to God's teachings. Their partner would not be permitted to enter my house as a partner and my child would not be permitted to see his/her partner. I would teach my child to remain celibate with every bit of effort I can muster. It would likely be difficult to succeed but what choice would I have? Loving a child would include wishing them eternal life in heaven not just temporal happiness.