"Innocent until proven guilty" only applies in a criminal trial. The man in question died in a shootout with police; he will never be proven guilty, because you can't put a dead man on trial. You can't libel or defame a dead man, from the point of view of the law.
There has to be a point where media can call someone a terrorist short of conviction in a court of law. You can argue that that point hasn't been reached in this case, but there has to be a point, since otherwise we'd have to call Bin Laden an "alleged terrorist."
As a very general comment as I do not know anything about the San Bernardino case, I think we need to apply extreme caution when using the word "terrorist" because of extreme, far-reaching legislation based on the broad definition of terrorism: https://en.wikipedia.org/wiki/Terrorism_Acts#List_of_legisla...
There has to be a point where media can call someone a terrorist short of conviction in a court of law. You can argue that that point hasn't been reached in this case, but there has to be a point, since otherwise we'd have to call Bin Laden an "alleged terrorist."