Replace youtube video player with a different div

I’m using Fiddler(web debugging tool) and the below code is JScript .NET, which is basically a .NET version of Javascript.

 if (oSession.HostnameIs("") && oSession.oResponse.headers.ExistsAndContains("Content-Type","text/html")) // oSession is a Fiddler object session
      oSession.utilDecodeResponse();   // Remove any compression or chunking
      oSession.utilReplaceInResponse('<b>','<u>');  // Search and replace in HTML

How do I replace youtube video player with this message?

<div id="player-unavailable" class="  player-width player-height    player-unavailable ">
                <div class="icon meh"></div>
  <div class="content">
    <h1 id="unavailable-message" class="message">
            This video is no longer available because of inappropriate content.
    <div id="unavailable-submessage" class="submessage">
Sorry about that.


Thank you