Reading Stranger in a Strange Land caused me imagine what it would be like to explain to a complete alien - someone who has no conception of gender, gender identity, or sexual orientation - about why we have a different set of rights (aka fewer) for people for these reasons. Trying to explain it out loud makes it sound completely and utterly ridiculous.
"Okay, you have two genders - male and female - that when they engage in intercourse at the right age and the right time of the month, then the female begins the process of procreation called 'pregnancy'. The process and result of 'pregnancy' is not assured.
People of both genders enjoy the act of intercourse, for both emotional and sensual reasons, even if they do not wish to procreate; therefore they take measures that prevent procreation while engaging in intercourse. We call these measures 'birth control'.
Most males and females feel naturally attracted to the other gender and so they engage in intercourse in a 'heterosexual' manner. Some males and females feel naturally attracted to their own gender and so they engage in intercourse in a 'homosexual' manner.
Some religions and cultural traditions believe that the 'homosexual' manner is not the 'correct way' to live because procreation is not possible. Within this group, there is a smaller group who is also opposed to 'birth control' for the same reason. These groups have used the democratic process to pass laws that give more rights to those who live the 'correct way' then the 'incorrect way'. That is why we have fewer rights for homosexuals."Try it for yourself. Say it out loud. Try to sound as fair and balanced to both sides as you can, while still being accurate and universal. I can't do it without making it sound silly, but maybe you can?