``Are you going to trust your company to some software written by pimply teenagers with no social life?''
This is an example of FUD method #2, outright fabrication. As such, the counter is simple: facts. The majority of Linux kernel programmers, for example, have more than ten years experience in the computer industry and one-fifth of them have doctoral degrees. Point the skeptical towards http://www.linuxgazette.com/issue33/bentson.html .
This counter also works for the ``I don't want to use some freeware written by a bunch of hackers.''