There is only so much room in the world.
If it is used to grow vegetables, enough
can be grown to feed the entire world.
If people continue to eat cow, there will
noty be enough space to feed everyone and
some people are doomed to starve to death.

Worse yet, rainforests are being burned down
to make room for the cows. This depletes the
oxygen in the atmosphere and contributes to
the greenhouse effect.  Soon we will run out
of rainforests and there will still not
be enough cows to feed everyone.  

The only sensible thing to do is to 
stop eating cow flesh.