There's only a "clear trend" on homosexuality if you limit your timeframe.

Attitudes toward homosexuality in ancient Greece, for example, were pretty liberal. They were also really different from anything we have today, such that it defies putting it anywhere on a spectrum that modern folks would be familiar with.

Society moves in many directions, often simultaneously, and we should be careful not to confuse the movement of the last century or so with either inevitability or rightness.

(I personally think that consenting adults should be allowed to have whatever sort of sex and marriage they feel like, I just object to the idea that there's a clear trend on the issue overall.)