Timothy McVeigh was Christian but you don't hear that being mentioned, unless someone is trying to make Christianity look bad, and that's the point with 9/11; yes the terrorists were Muslim but that's not the reason they did the attacks. People rush to conclusions when things like this happen because they are scared and they want to make sense of it. Another reason is that whenever a human being does something terrible like this other humans (non-muslims in this case) try to convince themselves that this person is different to them, that they themselves would not and could not do such a terrible thing. In reality we are all the same, we are all capable of terrible acts.
I am not starting a religious debate, I am stating the reason why religion should NOT be a part of this thread.
I hope they do build a mosque on ground zero, it would show a lot of maturity and decorum from the US. It's an ironic display of solidarity against Al Qaeda, the religion they claim to represent being celebrated on the spot they destroyed. I can't think of anything better to put there.