Sorry, too much research on biological basis for behavior suggests we do indeed have inborn propensities. Identical twins reared apart go into the same or similar lines of work far more often than do adoptive siblings raised together from birth. In case you hadn't notice, the brain is physical.
We all know that gross deformities of the brain (Downs syndrome, for example) have a genetic basis. Why are you fighting the obvious? Do you really buy the argument that inborn = morally right?
You are raising strawman arguments.
Yes, identical twins are similar in many ways, but not in the tendency to go gay.
Some things like Downs have a genetic cause, but some infections do genetic damage, so your analogy to Downs is not complete. You'd have to show that the genetic damage shows up only at the same rate as other bad mutations (which gay does not), or that being gay provides some benefit (like sickle-cell/malaria), which hasn't been found.
My reference is "Perspectives in Biology and Medicine", 43,3, Spring 2001, pg 406, the article is "Infectious Causation of Disease: An Evolutionary Perspective", by Cochran, Ewald and Cochran.
This article notes that the evolutionary fitness load and relatively high incidence matches that of an infectious cause, not a hereditary cause. It's not proof of an infectious cause, but it is sufficient evidence to justify further research.
First, I thinkg you misuse 'straw man': as 'straw man argument' is a feeble expositoin of the opponent's position which is then easily knocked down to produce a false rhetorical triumph.
The examples I gave (Downs and twin studies for the surprisingly complex, and usually though to be socially deteremined phenomenon of career choice) were in fact strong arguments first as a reminder of the physicality of the brain, and second that complex social behaviors can have a strong genetic component.
The were a propos of the post to which I was responding, and were presented as arguments against what I characterized as its tabula rasa attitude toward behavior, not as any kind of conclusive arguments about the behavior at hand.
You will observe I have nowhere argued for genetic determinism as a basis for erotic attraction, and have always spoken of propensities, or in posts dealing with moral judgement, besetting temptations.
Now, if 'homosexual' is defined behaviorally, one will flag only those who have acted according to the propensity, and thus will not get the entire population of those who have it, whatever its source.
And on what basis do you claim that there is no similarity in 'the tendancy to go gay'? I find no studies with large samples of twins reared apart (hardly suprising for a phenomenon with an incidence rate of about 3% in the general populace). The twin studies which have been done comparing siblings form the same household--all of which find a substantially higher concordance rate for MZ twins of homosexuals (52%) as compared with biological brothers (22%) or adoptive brothers (11%) (I cite only the most recent, Bailey & Pillard, 1991)-- cannot tease apart environment (including prenatal) and genetics, but suggest both play a role.