Wrong.
Mustafa al-Imam, a Libyan national approximately 48 years old, was found guilty of terrorism charges for his participation in the Sept. 11, 2012, attack on the U.S. Special Mission and Annex in Benghazi, Libya. Ambassador J. Christopher Stevens and U.S. government personnel Sean Smith, Tyrone...
www.justice.gov
Now true, it was not a consulate. That is because we had none, the US severed all diplomatic ties with Libya back in 1979. And the appointment of Ambassador Stevens was to be the first step in normalizing relations again. And one of the duties of him and his staff was to locate somewhere that they could create a new embassy. However, before that could happen the compound they had set up residence in was attacked.
Yes, there were no "Marine Guards", that is because they are normally only located on the grounds of an embassy or consulate. However, the State Department could have requested it as the compound was in effect the closest thing we had to such at the time. And the State Department was asked a great many times by Ambassador Stevens to increase their security. Which were all refused. He was refused Marines to secure the compound, and he was also refused additional security and was told to just work with what he had.