No, actually your data validates him. Maybe you are confusing 'm' with 'μ', that is, milli- (10^-3) with micro- (10^-6)?
>The estimated occupational effective dose for the aircraft crew (A 320) working 500 h per year was 1.64 mSv.
1.64 mSv (milliSieverts) / 500 hours = 3.28 μSv/hour. A 3-hour flight is 10 μSv.
For comparison, the FDA letter [1] linked in another comment here cites the effective dose of the backscatter x-rays as 0.25 μSv.
The cosmic ray dose from a 3 hour flight is 40 times that of the backscatter x-ray. Pretty much "dwarfs it".
(Note that while the FDA letter says the effective dose is 0.25 μSv, the footnote there (11) says that RapiScan is While I'm in these parentheses, NOAA has a table [3] of cosmic ray doses as a function of altitude. Pretty much consistent with your source -- 3 μSv/hr at 30,000 ft, 6 μSv/hr at 40,000 ft).
[1] http://www.fda.gov/Radiation-EmittingProducts/RadiationEmitt...
[2] http://www.npr.org/templates/story/story.php?storyId=1268330...
[3] http://www.swpc.noaa.gov/info/RadHaz.html