phrase usage - due to versus as a result of

According to the answer key of a SAT preparation book I'm studying, there is an error in the sentence

By the time the bank guard closed the doors, a riot had erupted due to the long lines and shortage of tellers.

and it should be changed to

By the time the bank guard closed the doors, a riot had erupted as a result of the long lines and shortage of tellers.

I disagree with this. Why is the first sentence unacceptable?

Answer

19th-century stylists held that due is an adjective and that due to X phrases should be employed only as

• a postposed modifier, as in A riot due to long lines erupted, or


• a predicate adjective, as in The riot was due to long lines.

Actual on-the-ground usage has long since transformed due to into a preposition equivalent to because of, and you may safely ignore this ‘rule’ in all circumstances except one:

When you're taking a test of your knowledge of English, assume your examiner follows the old rule: use due only as an adjective, and treat any other use as incorrect.

It’s stupid, but it’s a fact. As the poet Schiller wrote:

Against stupidity the gods themselves struggle in vain.