Al-Qaeda "sometimes" commits crimes against humanity

From The Guardian. The following was sent in my one of my readers, Daniel.

Amnesty International today claimed that governments and armed groups such as al-Qaida were putting human rights and international humanitarian law under the greatest pressure for more than 50 years.

[...]

It condemns attacks by al-Qaida and others as "sometimes amounting to war crimes and crimes against humanity" but says principles of international law that could prevent such attacks were being undermined and marginalised by powerful countries such as the US.

How can an Al-Qaeda attack "sometimes" be an attack against humanity? I'd like AI to supply an example of when an Al-Qaeda attack was not an attack against humanity.