"Terrorism has a political, religious or social philosophy behind it with which gives the killer a sense of moral righteousness that is shared by others of the same philosophy."

A better way to put it is to say that a terrorist has a wanted future in terms political structure and political arrangements. 

Think about two examples of white terrorists:

Quebec 1970s, separatists use kidnapping and murder as their terrorism tools, wanted future is separate Quebec.

Timothy McVeigh, Oklahoma City, he uses big bomb as terrorism tool, wanted future is shrinking government backing off on gun restrictions.

The word "terrorism" is silent on whether terrorism is an effective tool or not, for achieving the wanted future in question.

And the word terrorism is perfectly appropriate for the above white terrorists, just as it is perfectly appropriate for Islamist attacks in European cities.

As many have, one really has to question the columnist's motive, trying to re-define the word terrorism...