How Do We Know al Qaeda Wants to Kill Jews?

The Goldblog inbox overfloweth. This e-mail is from David Smith of Fort Lauderdale, in reference to my post on the motivation of people who mail bombs to synagogues from Yemen:

How in the world can you presume to know their motivation? Are you just able to sense from thousands of miles away that someone, whom you know nothing about, just wants to kill Jews because they're Jewish?
 
They may well have wanted to kill Jews purely because of Israeli policy toward Palestinians and for whatever reason found these Chicago synagogues opportunistic targets.
 
Do you have any idea how tired you are screaming anti-semitism every fucking week, almost always at the most nebulous of targets? It's like you have no reason for existing, other than to call people anti-semitic, no matter if there's any support for it or not. And taking on a nutcase like Pamela Geller. Is that supposed to absolve you and make your unsupportable allegations about anti-semitism valid?
 
Angry, angry!

Here's another one, from someone who identifies himself as Cliff from New Mexico:   

Goldberg, you must be kidding! Do you really think the occupation of Palestinian land by the Israeli army and settlers is irrelevant to al Qaeda actions? Israeli occupation is the main reason al Qaeda exists! If the Israelis had let the Palestinians have a state 20 years ago, Arabs wouldn't feel a need to join radical groups the way they do today! Watch al-Jazeera, the occupation is all they talk about!

And this one, from a person identified only as "Simpson":

It is important for Zionist propogandists such as yourself to argue that al Qaeda is antisemetic, but it is no more antisemetic then Hezbollah. They are not culturally prejudiced groups, but they are political, and politically what they stand against the most is the Israeli treatment of Palestinians in the occupied territories. Read their own literature, if you dare.