Because I don't think you can site any complying science to back up your opinion. Science shows that there is a genetic component but that that there is more to it then that. What the more to it is comes down to opinion.

I would rather have a senator I disagree with on why some is gay and evolution then one who I disagree with on spending and taxes. I don’t think government should try and regulate beliefs but I do need them to properly tax and spend. Public perception of social issues will change regardless of what congress does and that is where the real change is taking place. This is not like Civil Rights and public opinion is changing on its own. In the meantime I would like to not run the country into the ground with a bad fiscal policy.