Sorry — your response indicates exactly in which way I should have been more clear.

Using "teenage daughter having sex" to stand for something "obviously undesirable" assumes a lot about your audience. For one, it assumes that your audience does not contain any sexually-active teenage women; nor any sex-positive parents of teenage women; nor any sex-positive sex-educators or queer activists; nor anyone who has had positive (and thus not "obviously undesirable") experiences as (or with) a sexually active teenage woman. To any of the above folks, "teenage daughter having sex" communicates something not undesirable at all (assuming the sex is wanted, of course).

Going by cultural tropes, your choice of example gives the impression that your audience is made of middle-aged, middle-class, straight, socially conservative men — or at least, people who take the views of that sort of person to be normal, everyday, and unmarked. On LW, a lot of your audience doesn't fit those assumptions: 25% of us are under 21; 17% of us are non-heterosexual; 38% of us grew up with non-theistic family values; and between 13% and 40% of us are non-monogamous, according to the 2011 survey for instance).

To be clear, I'm not concerned that you're offending or hurting anyone with your example. Rather, if you're trying to make a point to a general audience, you might consider drawing on examples that don't assume so much.

As for alternatives: "Simply try to prevent your house from being robbed" perhaps? I suspect that a very small fraction of LWers are burglars or promoters of burglary.