How to delete a irrelevant facebook comment from my website(Asp.net)

See more:

Facebook-API

How to delete a irrelevant fb comment from my website. What i am doing is as:

 <div id="fb-root">
    </div>
// making myself as admin :

<script>    (function(d, s, id) {
        var js, fjs = d.getElementsByTagName(s)[0];
        if (d.getElementById(id)) return;
        js = d.createElement(s); js.id = id;
        js.src = "//connect.facebook.net/en_US/all.js#xfbml=1&appId=MyID";
        fjs.parentNode.insertBefore(js, fjs);
    } (document, 'script', 'facebook-jssdk'));</script>

Placed where i want FB-Comment box to be rendered:

My basic question is how can i delete a comment which is vulgar and publicly visible ? Although i have set myself as moderator in tools then also i am not able to delete other people comment(facebook) from my website i can only mark them as spam but others can easily see the comment on thier individual login. Thank You