People are not mere "things".

[IntravenousDemilo]

It's not, "the policeman that responded to the alarm," but "the policeman who responded to the alarm."

It's not "a liberal is someone that believes in liberty," but "a liberal is someone who believes in liberty."

It's not "the suicide bomber that blew himself up the other day," but "the suicide bomber who blew himself up the other day."

It's not "it's Limbaugh that is the drug addict and O'Reilly that is the sexual predator," but "it's Limbaugh who is the drug addict and O'Reilly who is the sexual predator."

When referring to people, "who" must be used to the exclusion of all other relative pronouns, i.e., "that" and "which". The corollary of this is that when "who" is used, it must refer to people, and not to other life forms or to inanimate objects. Thus, it's also not "my dog who turned 17 last month," but "my dog that turned 17 last month."

So we have a relative pronoun ("who") that is absolutely proprietary to the human race and no other, and that's because people are just so damned special, even when their grammar sets my teeth on edge. Some of these people (*cough*DavidGergenBrianWilliamsKatieCouricPracticallyEveryoneElseInTheMedia*cough*) are actually paid exorbitant amounts of money to (mis)use language. It's one of the most shameful aspects of our times.