Why is islam such a dangerous foe of liberal democracies?

Because of  the teachings of the koran stand contrary to them.

The music is irritating but the video reveals what I’ve been saying forever: the koran itself – and not a ‘few bad apples’ who mistakenly take its teachings too seriously – is incompatible with Western liberal secular values.  Pointing out this fact does not make one a racist or an islamaphobe. It makes one a realist who is awake and aware.

Sam Harris makes a very good comment on it here as does Jerry Coyne here.