My favorite response to, "When are you going to have a child?" When Johnny Depp offers to sleep with me.
I can't tell you how many people assumed my youngest daughter was an accident because we already had one of each! People even asked me if she was an accident in FRONT OF HER!
I have a friend whose parents referred to her sister as "the accident"! And worse, the youngest sister was referred to as "then we tried for second boy to even things out but got another girl".
...it's all about my husband being killed and him never returning home and that there will be nothing left of him for her to love.
Shall I come out and slap her for you? Goodness gracious, like you need to hear nonsense like that. She needs a filter!
Most people do have children, and most people do not find a simple question to be offensive.
I think that maybe you could look at how many people felt that the whole line of discussion can be offensive, and think about not going down that line of questioning next time you're with someone you don't know. It might be more offensive that you have considered it to be...
This reminds me of something one of my co-workers said the other day: "No" is a sentence - you don't have to give an explanation. Love it!
It's true! "No" is a complete sentence!
I think there's a big difference between asking someone if they have kids and asking someone if they are going to have kids (or worse yet, when they are going to have kids).
Absolutely! Do you have kids is so different from WHEN are you going to have kids.
Now I personally do the "overload them with information" method, when I'm asked annoying questions... Why DS has such interesting eyes, or the questioning looks seeing DH's black hair and obvious part-Asian features vs DS's on-the-surface-Irish looks, are answered with veritable essays on how interesting genetics is, and who, exactly, in the family has red hair, and why no one shared that info with us beforehand, and how rude people can be about it (hubby was once told "you look as though you STOLE that child" while standing with baby, my purse, babysling, and my jacket outside a women's dressing room). If we're going to have more has been answered with "we want more but it hasn't worked yet" and will soon be answered with some details of a pituitary growth we just found out about with hubby, if he gives me permission to get into the nitty gritty with those IRL.
You do find out who is and is not *listening* to you when you give real answers...a neighbor asked if DS is an only, I said yes and that we wanted more but it hasn't happened yet...and then she went on for minutes talking to DS about what kind of sibling he wants, how great it will be, etc etc...she asked a question and hadn't LISTENED to the answer.
OK I don't mean to go on, but I just think the questions people ask are amazing! And like I said, my method is to make 'em sorry they asked (OR make them happy they asked, depending on what sort of answer they really wanted) by overloading them with info, so I guess I just do that in these replies as well.
The "NO" with a stern face, or sometimes a sardonic laugh, has worked VERY well for my brother, by the way. He doesn't give ANY info out to such questions, though he can now refer to my son and his wife's new niece, as being all the kids they need, and I recently got a joke about how they were thinking of adding a third *cat* to the household but it seemed like too much work, when I told him that a family friend had triplets...but for strangers, the NO (and a look of death if they continue) has served him well.
This reminds me of some friends of ours. When my MIL met them and asked "do you have kids?", the husband said "no, but we're trying real hard!" 
