I think it is a timid article. It doesn't use the term state terrorism to refer to the actions of the imperialist powers.

Also, yes, "the public" is also responsible. The public could be responsible for a positive change as well as for perpetuationg atrocities and the status quo, if not through tacit support, it is through passivity, indifference, silence and acceptance. 

The public votes for the same criminals in again and again. Is not that a responsibility? The public also votes for the same criminals to perpetuate crimes at home (plunder, privatisation, inequality, etc).

Furthermore, the author has not cited "the roots of terrorism" in the plural. He is happy to mention only a couple of the roots.

The roots of terrorism