In the JFBCSystem plugin file at /plugins/system/jfbcsystem/jfbcsytem.php, in your version around line 287, the following call will add the Open Graph tags to the page:
$this->replaceGraphTags();
If you go into that method, you can see the following method calls that will generate the lists of tags to add to the page. So either you can skip the entire function all together, or you can comment out the appropriate ones:
$openGraphLibrary->addOpenGraphEasyTags($newGraphTags);
$openGraphLibrary->addDefaultSettingsTags($defaultGraphFields);
$openGraphLibrary->addAutoGeneratedTags($locale);
-Melissa