Is it appropriate grammatically/linguistically, not necissarily
politically, to say "They had homosexual sex" or
"They had incestuous sex"?
 
If it is appropriate grammar, is the adjective
homosexual being applied to the act in question (that
 being sex)?
 
If it is being applied to the act, or instance of
the act, why is it revealing qualities of the actors? 
In the case of homosexual, the gender's of the actors
are revealed by the adjective that is applied to the
 act.  Is this an anomaly for an adjective?
 
Are there other adjectives that are applied to acts,
 or instances of acts that reveal or imply
 charactaristics of the actors?  Could you give
 samples?

The only other instances of adjectives that can seemingly be applied
to an action but reveal traits about the actors, that I have found,
are heterosexual, and incestuous.

Am I using these words correctly?  Are there other such adjectives? 
Is my interpretation of how the words are applied, and what the word
imply incorrect?

In the answer, please cite references that will support the proper
linguistic/grammatical useage of the word homosexual in particular and
of other such adjectives in general.

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Clarification of Question by bdmarti-ga on 12 Jul 2005 06:38 PDT

I would really like some authoritative sources that can tell me the
proper linguistic/grammatical manner to use the word homosexual.

Strange that you haven't received a comment or answer to your interesting question.

Yes, you have used homosexual and incestuous correctly, grammatically,
at least.  The adjective does apply to the action, and does say
something about the persons.
In most contexts, it would already be apparent who "they" are, so that
saying or writing that "they had sex" would be sufficient without the
adjective.
(But as the opening line for a short story, the sentences would be
pretty powerful.)

It is intriguing among this community of wordsmiths that no other such
adjectives came to mind  - not to me, either, especially when trying
to find examples that were not closely related:
"She gave her a sisterly kiss."   They wouldn't have to be sisters.
"He gave him some avuncular advice."   He wouldn't have to an uncle.
"His employing the young man was a nepotistic action." 
    Would one in ten assume that he had hired his nephew?

"She gave her some motherly advice."    Yes, probably we would all
assume that they were mother and duaghter.

Ditto for "fatherly".

But that is getting away from a common action, ...

I give up.  You may indeed have found that these two word are unique
in this respect.

thanks for your comment myoarin.

I was surprised I didn't get any answers.

Motherly/fatherly come close, but they don't seem the same, as the
implied qualities are more abstract.

thanks for the thoughts though!