I am very much a supporter of religious freedom and as such I support the people of Islam. But as the OP is illustrating, it is a point of fact that in terms of the accepted definitions of terrorism, Islamic Extremism is overwhelmingly the greatest threat.
In the 1970s and 80s events that occurred symbolized the object of discontent eg the Bombing of the US Embassy in Tanzannia or the attack on the USS Cole. But that has now shifted to attacking the general populace. Here the idea is that no longer is it necessary to attack major targets eg The Twin Towers in the USA. Those types of events are complex to organize with significant security risks in order to achieve success. Instead the ambition is to provide the lowest of security events in random areas resulting in a more major impact on a nation, not so much in terms of casualty count, but rather on the national psyche whereby the psyche outcome is "nowhere is safe".
Also the methodology has changed. In the 70s and 80s hijacks made major news but this fell away with the advent of greater security measures. Instead what emerged was overwhelmingly a trend towards bombing. This was easier to obtain, caused a significant casualty count, and could be aimed at a symbol of discontent eg a synagogue.
In the new millennium abductions became common as well. Partly to publicize a cause but more commonly as a form of revenue raising. Now what we see is methods of lowest sophistication eg use a car to ram people. The organizations are now at pains to devolve the organization of event ie dont form a group... dont discuss it with anyone...just do it. This makes it very difficult to provide security surveillance when there are no cells to surveil..just a myriad of individuals.
But to the OP - as much as I dislike anti islamic sentiment, the OP is quite correct - Islam is very much the principal terrorist security risk
