It's not ridiculous. It is the very core of the gay/straight argument. Doing what you want in the privacy of your own bedroom is fine, once you take it out of the bedroom is where it becomes an issue. People have every right to object to this.
As for the apples to oranges, no, it ins't, it is still talking about what is considered morally acceptable in our society. It is morally acceptable in other societies to kill your children does that make it wrong there too?? Our society as a whole, however, has decided that it is NOT ok to do this but what if there was a movement to change this just like there has been a movement in recent years to "accept" the gay lifestyle. Not to turn this into a religious post but even the Catholic church accepts gay people, they do NOT agree with the gay sex--that is a HUGE distinction. Our society as a whole has not decided that the gay lifestyle is morally acceptable. People are trying to change that.