It was an act of war by Islamists from Saudi Arabia, backed by the tyrannical regime in Afghanistan against the USA, Western civilisation and secular free liberal society.
The battle is far from over, but the success has been to prevent a repeat attack in the US - although it has happened in the UK and Spain, more by inspiration than by direct control.
Islamists are stone age thugs using 21st century tools, they are one of many direct threats to the advancement of humanity, and the lives of those who wish to live peacefully and not initiate force against others. They must be fought both philosophically through the battle of ideas, and directly where and when they threaten freedom and lives.
That is why keeping Afghanistan and Iraq out of Islamist control is so important - the best examples to the Muslim world are secular states that allow pluralism and are at least partly free. Sadly, Turkey and Bosnia are the best there is, whilst most others are either oppressive or unable/unwilling to deal with their own murderous Islamists.
9/11 was not just an attack on the USA, it was an attack on the idea of the USA - a secular liberal free society where people can live their lives as they choose, without being forced to bow to any religion or political beliefs. To appreciate that you need to accept that secular liberal society is superior to theocratic autocracies of all kinds - to do that tolerance of individuals practicing Islam peacefully has to be separated from those using Islam as the foundation to wage, threaten and plan for civil war.
I do not care if individuals are Muslims and treat religion as a basis for how they live - until that extends to taking away my individual freedoms and attacking me. I don't like Islam, but there is a clear line between:
- Hating Islam as a philosophical and belief system;
- Fighting Islamist inspired attacks and threats; and
- Defending the right of someone to worship the Muslim faith whilst not posing a threat to anyone else.
Few disagree with the second point, few argue the first and not enough who argue the first also defend the third.