the line that best illustrates the cruelty and heartlessness with which the jews were treated with during deportation is

I think you can choose from a number of quotes. Consider this:

The Hungarian police made us climb into the cars, eighty persons in each one. They handed us some bread, a few pails of water.

This quote really illustrates cruelty when you think about it. Little air, little food, no bathroom and no escape from these cattlecars.