When they discover a plot by do-gooding aliens to destroy human sexuality (in the mistakenly belief that it causes war on Earth), Nerdy Sid and Zen must save the world’s libido.

You're right, the parenthesis isn't needed in the logline. The aliens don't see the effects of their plan because they are bad anthropologists caught in the headlights of humanity's own obsession with sex. When they take human form they adopt the shape of a celeb couple (Price/Andre). It's satire, not adventure. I hope it's fun!

Thanks - makes me think I should up the fact that Sid is lovelorn, and Zen sex-starved

The part in parentheses throws me off. Grammar aside, I wonder how the aliens won't see the terrible long-term effect of their plan. Could they just be looking for a non-violent way to eradicate the human race over time? Just a thought. I think you're onto something fun here.