Bit before my time, but I was aware of these atrocities being carried out in Germany at the same time as Palestinians were hijacking aeroplanes and such like. And of course, I wondered what exactly their problem was. Not democratic rights, for sure. And indeed, they were mostly middle class.

From http://www.spiked-online.com/index.php?/site/article/5919/ I understand now that they were radical leftists who weren't content to support the unions against the capitalist exploitation of the working class. They felt that social reform was just a way of playing along with the existing political system. So by causing upset and mayhem with kidnappings and bombings, they expressed their contempt for modern capitalist society, and hoped to provoke conflict, which might then bring about a revolution.

Contempt is the key concept, isn't it? Terrorists can justify slaughtering people, even innocent bystanders, because in their minds these victims don't qualify as human beings.