On the one hand I can understand the point behind it. By defining a specific sect of the religion, with the way morons are in the world today, they'll lump all people who are Shia into that group, but not all who practice Shia are terrorists. Besides, how many people really do know the difference between the sects? I mean, there's more than just the two big ones. (
https://en.wikipedia.org/wiki/Islamic_schools_and_branches )
Focusing on what terrorism is, is the point.
On the other hand a lot of Islam extremists do come from that sect of Islam. With all the different sects, knowing which one is the problem is knowledge people should have.
But same could be said of Jewish terrorism (
https://en.wikipedia.org/wiki/Jewish_religious_terrorism ) and of course the 'lone wolf' Christian terrorists...
I think in the end, the focus should be on terrorists. The religion they come from should be considered only after the fact, as it pertains to that religion's influence upon the terrorist as a push to commit the crimes they have.