Hello, I have had the same issue, the Facebook intergration with ioOS displays all the facebook events in the calendar - which can be a real pain if you have lots of events.
I have not found any option in iOS6 to filter by accepted events or to hide declined events. This is something Apple should really work on - sounds to me like they just bundled this into iOS6 without consideration for accepted or declined events.
So the workaround which I have found is to stop the facebook calendar in iOS6 (Settings/Facebook) and instead to subscribe to Facebook events and/or birthdays via the site straight into iCal. What is in your iCal will appear on all your devices so there you go. Make sure in FB to state that you don't want al events to be displayed. Then you'll be fine.
Use this link if you want http://www.wikihow.com/Sync-Facebook-Events-to-iCal
Make sure to go to the settings option on FB page to select which events you want displayed.
It lacks the neat little FB icon that would appear via the iOS intergration but lets hope Apple sorts this out quickly and that we'll be able to chose which events to display, accepted or rejected etc....
Hope this helps,