Learn English – Meaning of “scared the hell out of someone”

This construction is usually (or often, anyway) used in team situations:

There were more of us than there were of them.

"More of XX" meaning more people on the team. However, it is also used (perhaps ironically/humourously) when one team has only a single person. In that case, there are always more of them than of him/her.

To talk someone out of something means to "persuade someone not to do something". A related phrase is to talk someone into doing something, which means to persuade them to do it.

In this context, Jubeir is trying to persuade the mutawwa not to punish the writer for wearing what they considered indecent clothing. Apparently the persuasion was difficult, for Ms. Dowd records that it "took a surprisingly long time".

And yes, talk someone out of something is a rather popular idiom, used in many contexts.