A website is trying to play my wordpress videos in an iframe

Hi:

Some folks want to play my wordpress blog site’s videos from their site using an iframe reference back to my wordpress blog. The video’s play badly and I have asked them to stop, but they have chosen not to stop. So I added the following code to display a copyright violation within their iframe. It’s not very effective, can anyone else suggest a way to block this type of reference to a wordpress blog site that is more iron clad?

<?php
//iframe misuse test inside my template's header.php file

if(isset($_SERVER['HTTP_REFERER'])) {
	$this_referer =  strtolower($_SERVER['HTTP_REFERER']);
	$invalid_referer = "hackersite.com";
	$this_referver_pos = strpos( $this_referer, $invalid_referer);
	if ( $this_referver_pos == false) {
   	 // valid server reference to this site
	} else {
		echo "<h1>Warning: Possible Copyright Violation</h1>";
		echo "<p>Contact the owner of this site to report misuse of copyrighted material.</p>";

		exit;
	}
} else {
	// link not referred
}
?>