There are studies that cover statistics. The number of deaths from turbulence in the US from 1980-1993 totals 3 - though the number of (sometimes serious) injurious was 600+ during that same period. It is not indicated how many unrestrained infants were injured - though logic would indicate very few (but likely more than zero).

With an estimated 10 million flights in the US alone each year - the chance of serious injury or death are thus considered a statistical zero and not something to overly worry about.

That said - if it were your kid it would represent 100%.

If you need the peace of mind or like the comfort of a car seat - I say great. But admonishing other parents by (inadvertently) overstating the risk, I don't agree with.