Just a couple of comments from a non scholar
1. The harshest surah in the Quran, Surah At Tawba, starts with a declaration that the treaty between the Prophet and the Mushrikeen will be cancelled in four months, and then goes on to declare war with after that time. IT DOES NOT GIVE PERMISSION TO START WAR WITHOUT THIS OPEN ANNOUNCEMENT, EVEN THOUGH THE MUSHRIKEEN HAD BROKEN THE TREATY. And the surah goes on to speak about the importance of treaties. So anyone who is belittling the importance of treaties in Islam is going against the opening message of the harshest Surah of the Quran.
2. I see so much hate, anger and impatience in some of these posts. People who write such posts should perhaps read the story of the Prophet(SAW) when he was in Taif. And also bear in mind how little there is is in the Quran about muslims being opressed, and when this topic is mentioned, it is usually to address muslims to be patient. If the Prophet(SAW) had shown the anger and impatience I see in some of these posts, Islam would have been destroyed before the hijrah.
3. One thing which the likes of Al Qaeda totally ignore is the fact that we muslims are in the best position in the history of Islam to give dawah. The west has basically given up on religion in general and Christianity in particular, and the people WANT to hear about Islam, and WANT to know if it's the truth. Instead of wasting time by writing angry posts on message boards, I suggest that if you want to make a difference in the west, join one of the many dawah groups (I personally recommend whyislam.org) and do something beneficial with your time.