"as Dr. Siegel put it, sleepers are less vulnerable to harm than they would be if they were out on the street late at night"
Circular reasoning. If people didn't need sleep, there'd be just as many people on the street as during the day and it wouldn't be any riskier.
"argues that sleep evolved to optimize animals’ use of time, keeping them safe and hidden when the hunting, fishing or scavenging was scarce and perhaps risky"
... so if all the animals are asleep at night, we should be awake then, right? We can just walk up and bop them on the head from behind, Halo-style. Why don't lions hunt at night if it's got anything to do with that? Moreso, why does any creature at the top of its food chain need to sleep?
It's hard to imagine any scenario when asleep humans are more safe at night than awake humans. Even if there were giant nocturnal monsters all over the place, they could just hide .. in the same place they would be so safe sleeping, say.
Very unconvincing.