When you restrict travel with a quarantine, it costs.
Perhaps you restrict a sick child from going somewhere else where they need lifesaving care.
Perhaps you prevent a child from escaping an abusive situation.
Any economic cost is potentially fatal on the margins.
If the quarantine only saves one life, it may not be worth it.
There are enough people with severe adverse reactions to vaccines, for example, that you have to balance costs and benefits.
It is easy to consider obvious benefits and to ignore less obvious costs.
I was pointing out the human tendency for that.
In a way, it was a parody of liberal logic.
I am wary of any argument that says "If it just saves one life..."
"If a quarantine saves just one child's life, it's worth it." was as well.
The left was fond of using that phrase to push their agenda.
If banning eating meat saves...
If confiscating all guns saves...
If eliminating private cars saves...
Curiously enough, "If stopping abortions saves just one child's life..." was said by no liberal ever!
Turn their language abuse against them!