There are three logical answers here:
(1) The action is not wrong.
(2) Gay sex can never be an intimate expression of love and trust, though it might seem like one – this is Peter Plato’s answer above.
(3) Gay sex is a type of action that could be an expression of love and trust, but it is nevertheless harmful.
To give an example of another action in Category #3, consider the actions of two friends who spend lots of time drinking together in camaraderie. This could certainly be an expression of their love and trust, but it has the result of making them alcoholics – of making them, eventually, miserable.
I don’t know if gay relationships are strengthened or weakened by sex. I suspect the latter, but I don’t know. I can tell you this: if God genuinely forbids gay sex, there have to bad consequences to it. This doesn’t necessarily mean it is selfish or lustful, but it does mean that it either manifests some kind of vice or leads to bad consequences.
Well, I don’t need it put in perspective, because I’m attracted to other men. I will say that, from my limited experience of the sort of acts involved in gay sexual relationships, these acts aren’t the type of thing that lend themselves to total self-giving. They are … lopsided. If I were exclusively gay, I would find it frustrating that (to put it as delicately as possible) none of the acts involved naturally involve both partners’ erogenous zones at the same time.
Then again, it also probably makes chastity easier.