Military pilots go through basic training, are trained to use their side arms
much more than these pilots, would never fire their guns in their planes and
only have them for the chance that they bail in hostile territory. Commercial
pilots would be carrying guns in huge, pressurized tubes, full of PAX, that
will be substantially harder to fly with a hole shot in them. Additionally,
there are as many as 400 PAX on the plane who are in danger if you have a gun
fight on a loaded plane.
As far as guns protecting property, they take property even more.
Additionally, the back and forth we have in the US with guns, coupled with our
culture that preaches fear and consumption means that guns kill more people here
than the rest of the industrialized world combined. It is this same thinking
that makes people think that we need to give pilots guns, further endangering a
plane. With the new cockpit doors, there is pretty much no way for someone to
get in if they are not let in, so the pilot can put anyone not buckled in on
the roof, knocking them out, much faster and more safely than taking them out
with a gun. Remember, they take care of property just fine in the UK where
beat cops don't even carry guns (and are on much less of a power trip and have
better attitudes).