Incest is sex between blood relatives
Polygamy is marriage with multiple partners.
Both are acts
Homosexuality and heterosexuality are sexual orientations- not actions.
That you cannot tell the difference between a man having sex with his daughter- and 21 year old man being attracted to other men- is both disgusting- and not surprising.
You're being willfully dishonest, creating a distinction that doesn't exist.
All of these are deviant desires, on which one may be tempted to act.
A man may be sexually-attracted to his daughter.
A man may be sexually-attracted to another man.
Either man may or may not act on these attractions.
There is no meaningful difference between a man who has one deviant sexual attraction, and a man who has another, if both do not act on them.
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