With the Klingons, it'd be a bit problematic, considering that any attempt to initiate a mating ritual would be interpreted as an attack by another male Klingon—unless, of course, it was delivered with a bit of that far-famed Klingon love poetry. 
Perhaps that's the only time it's acceptable to flee from battle, eh?
"Huhr?!"
Other than the Dax/Khan kiss (which could be dismissed as residual affection derived from a heterosexual relationship), we have little overt evidence of homosexual behavior in Star Trek, which could mean any number of things, in universe, such as:
I do think various undercurrents of homoeroticism were subtly woven into the Trek tapestry, though: The Seven of Nine/Janeway, Reed/Hayes and Garak/Bashir relationships seemed to possess certain elements that could be interpreted as sexual interplay or tension—though that's certainly not the only way to interpret various of these interactions.

Perhaps that's the only time it's acceptable to flee from battle, eh?
"Huhr?!"

Other than the Dax/Khan kiss (which could be dismissed as residual affection derived from a heterosexual relationship), we have little overt evidence of homosexual behavior in Star Trek, which could mean any number of things, in universe, such as:
- It's entirely a non-issue and completely acceptable under IDIC, but not particularly widespread
- It was a uniquely human genetic aberration that died out as man began to tinker with his genome—subtly (or not-so-subtly) discouraged so as to aid children in avoiding a still-prevalent stigma; in addition, I certainly think gays might have been targeted during the Eugenics Wars, and those of Colonel Green
- It proved correctible with advanced medical and/or psychological techniques
I do think various undercurrents of homoeroticism were subtly woven into the Trek tapestry, though: The Seven of Nine/Janeway, Reed/Hayes and Garak/Bashir relationships seemed to possess certain elements that could be interpreted as sexual interplay or tension—though that's certainly not the only way to interpret various of these interactions.