The article wasn't taking issue with the conceptual idea of derailments— people operate freight trains; they carry huge loads of toxic chemicals through populated areas; the environment can be impacted.

However, the author didn't definitely show that insanely long trains increase these dangers. They seemed frustrated that driving these trains sucks and talked about how frequently derailments occur and seems to believe the two things are related. The NHSTA numbers seem to indicate the trend for derailments is going down? Perhaps as train size increases, the number of trains decrease and the risk to the individual conductor goes up? Don't know enough about the subject matter to knowledgeably infer an answer, so I won't.