Sorry to be pedantic Guy but the centre or perhaps more correctly the focus of worship for devout Muslims is the Kaaba (Arabic: الكعبة ) where most Muslims hope to visit at least once in their lives ie. to go on a (the ) hajj
cheers Bob

This is not necessarily a position only shared by violent extremists. I believe it is common among some peace-loving Eastern cultures (I know this to be true of traditional Tibetan Buddhists and the Parsis of India). Attachment to the dead is not encouraged (for their sake as well as for our own), their belongings are distributed among the living, their bodies are burned, or broken up and left for vultures (sky burial http://relijournal.com/religion/feeding-human-corpses-to-vultures-sky-burials/) or other animals to consume.

The attachment of the living to the dead has been identified in several (at least) cultures as an impediment to journey the dead person needs to make. I am thinking especially of an old English folk song ‘The Unquet Grave’ made famous by Joan Baez:

http://www.mp3lyrics.org/j/joan-baez/the-unquiet/

I’ll do as much for my true love,
As any young girl may,
I’ll sit and mourn all on his grave,
For twelve months and a day.

And when twelve months and a day was passed,
The ghost did rise and speak,
“Why sittest thou all on my grave
And will not let me sleep?”

Yeah … I know this has not great relevance to the activities of Mohammed Atta. Just wanted to point out that ‘leaving the dead alone’ is not necessarily a marker of extremism.