WTF? Just a wee bit snarky, aren't you?
In California, a fairly high proportion of libertarians don't have kids, but that was not the case when I lived in Colorado or Tennessee, and my gut feeling is that libertarians in most other states have families (at least where they're able to meet and mate with people similar to themselves).
I'm a libertarian. Children are not an "existential threat" (whatever the h3ll that means); but nowadays they are a choice, not a duty. Remember, this is the 21st century? We have such modern contrivances as contraception. We don't *have* to have a kid every nine months or so.
For those who want kids, having and raising them is a job, a hard job, and sometimes a joyous job, and I wish them well. For those who don't want kids, they can be a burden.
And for those of us who'd like to be able to go to restaurants without having to deal with continuously screaming children whose parents won't shush them or stop them from running around, other people's kids are a pain in the @$$, not a joy.
"And after 9/11, there is no longer any doubt that today America faces an existential threat to our security -- a threat as great as any we faced during the Civil War, the so-called "Good War", or the Cold War."
-Condi Rice, Oct. 1 2002
Contraception, by separating sex from its reproductive and unitive purposes, makes marital sex similar to self-abuse or homosexual liasons, hence my amused snark.