Meet Simile and Sui Generis.
Simile, to refresh memories, is a favorite rhetorical device of writers that compares two essentially unlike things that nonetheless have similar characteristics: The quarterback was like a locomotive.
Sui generis, the Latin phrase meaning unique or one of a kind, is a helpful restraint upon the former. Some things, even if they share certain characteristics, shouldn't be compared. Sui generis is the braking system on a rhetorical locomotive, or at least it should be. That was a metaphor, by the way, and not a very good one.
We in the news business could stand to apply the brakes to our runaway impulse to "similize." I personally love a good simile, which is often a way to inject levity into a column. But lately we've seen instances of simile-itis that might have saved readers and viewers some angst, even if writers and pundits were left with less to say.
In the past several days, we've heard news people and others compare Obamacare to Katrina and Iraq. Sarah Palin compared our national debt to slavery. Countless times in recent years we've seen "Nazi" applied to people with whose policies or politics we disagree, none so frequently as George W. Bush, though President Obama, too, has had a few turns.
All of the above are clearly sui generis and should be retired from any future similes unless they are referring to truly like things, not just a single person's impression of the world while musing on current events. Katrina is like Sandy because they were both natural disasters, though significantly more people died in Katrina than in Sandy. Iraq is sui generis and nothing like Vietnam, to which it was sometimes compared.
Nazis and the Holocaust shouldn't be compared to anything else. The systematic, state-sponsored extermination of 6 million Jews, as well as others, is sufficiently horrific to stand alone. Pro-lifers who sometimes characterize abortion as a Holocaust are probably not helping the cause of revelation.