Slow down a little with the number of posts Razgriz , I post one reply only to see you have posted three more!
They may be Muslims, and many Muslims may condemn them by saying they are not "true Muslims" because their understanding and teachings of Islam are very different to the people who commit atrocious crimes behind the veil of their religion. When the IRA commit crimes in the name of Catholicism (or for it against a protestant north), I don't see them labelled as "Christian terrorists" or "Christian extremists". The entire Christian world are not responsible, do not need to apologize or in any way agree with their actions. Why is Islam tarnished in this light? Mostly because of anti-Islamic propaganda in general, and the media. Also a lack of understanding or knowledge regarding the subject. The Libyan council would need to come out in condemnation, but I can assure you the 110 million Muslims in India, the 60 million in China, or the 1 billion on the planet did not agree with these attacks, and do not need to apologize for them.
Same with Jain extremists in Hinduism, who make a minority, or "Zionists" by Jews across the planet. When Stalin/Mao committed acts in the name of Communism, they were not representing the beliefs of Marx or Lenin, but the portrayed it as such. It became East vs West, and the West capitalized on this with the cold war. The same can be seen of Islam currently, you might want to take a look at the clash of civilizations by Samuel Huntington. http://en.wikipedia.org/wiki/The_Clash_of_Civilizations
Looking at history, IR, (Hitler's propganda tactics), it is quite obvious to see what is happening at the moment.
I have already explained, someone who is a Muslim must adhere to the five pillars of Islam, that would technically make them a Muslim. Same as how a Christian must accept the holy trinity and Jesus Christ as the son of God. Like the 10 coofftopicndments, and the seven deadly sins. There are also 70 major sins in Islam. (First google link to give you an idea). http://www.allaahuakbar.net/important_issues_of_islaam/major_sins.htm
2. Murder. (Major sin).
29. Committing suicide (Suicide bombing is a major no no).
If you want to get an idea of what motivates the likes of Osama Bin Laden and a lot of Wahabis, if you can get your hand on Milestones by Sayyid Qutb, he is seen as the father of "Islamic fundamentalism". Is someone who is idolosied by the likes of Al-Quaeda and Bin Laden, his views and this book was so controversial, on it's release it was banned in the 60's in Egypt and many other predominantly Muslim countries, but grew in popularity amongst "Muslim intellectuals" as most banned works do. http://en.wikipedia.org/wiki/Ma%27alim_fi_al-Tariq It is a very philosophical book, very difficult to get through and quite powerful, it's Hitler's Mein Kampf only better written with Philosophy and History and twisting of the Qur'an and Hadiths. This is usually the book where anti-Islamic sentiments, quotes from the Qur'an are taken, this would be your best counter argument.
If you take a look at Shariah law, the Khilafah, the history of Caliphates, the Qur'an, you may understand it better as a religion of Peace. Many scholars claim so, Imams and Aleems in Islam do not have a higher power like priests and cardinals may have in Catholicism in regards to the Pope. So there are differing views and consensus depending on the school, but predominantly they preach peace. Take it as you will, if you want to take a look at some of the violent history of Islam, again look at the Rashidun and the Calpihs, a good read would be the book Letters of the Prophet, actual letters sent by Muhhumad to other world leaders at the time. The Jihad that was then, and the spread of Islam, http://en.wikipedia.org/wiki/Muhaofftopicd's_letters_to_the_Heads-of-State
Here is an E-copy on a quick google search for it http://www.kalamullah.com/Books/The%20letters%20of%20the%20Prophet%20Muhaofftopicd%20to%20the%20Kings%20beyond%20Arabia.pdf There is no copyright or intellectual property in Islam, so it is legally available to share.
I hope this clarifies some of the things for you?