I'm sure this is a good script for someone who doesn't want all of their Facebook events in their GCal, but there is a method for getting all of them in automatically:

1. Go to the Events page.
2. Click "Export Events" at the top of the page.
3. A box with a ical link for exporting to GCal, Outlook, iCal, etc. will pop up.
4. Take the link and add it as a calendar in the software of your choice.

The downside is that this gets every event that you have said yes or maybe to, so it can get crowded, but you can always copy the events you always want displayed to your personal calendar and turn off the Facebook calendar from displaying.