Cancellare cookie

[Adenina]

Probabilmente a voi sembrerà una banalità, ma io sto impazzendo

Sto cercando di adeguarmi alla cookie law.
Ho preso e modificato leggermente il codice per creare il banner da qui: https://www.cookiechoices.org/

Ho aggiunto in fondo una piccola funzione (delete_cookie) per fare in modo che l'utente possa cancellare il cookie, lasciato dall'accetazione sul banner, cliccando su un determinat link nella pagina della Cookie Policy.
Non mi riesce in alcun modo di cancellare questo benedetto cookie.

Vi posto il codice:

(function(window) {

  if (!!window.cookieChoices) {
    return window.cookieChoices;
  }

  var document = window.document;
  // IE8 does not support textContent, so we should fallback to innerText.
    var supportsTextContent;
  try{
    supportsTextContent = ('textContent');
  } catch(e){
    supportsTextContent = false;
  }

  var cookieChoices = (function() {

    var cookieName = 'displayCookieConsent';
    var cookieConsentId = 'cookieChoiceInfo';
    var dismissLinkId = 'cookieChoiceDismiss';

    function _createHeaderElement(cookieText, dismissText, linkText, linkHref) {
      var butterBarStyles = 'position:fixed; font: bold 1em \'Open Sans\', sans-serif; color: white;width:100%;height: 70px;background-color:#666;' +
          'margin:0; left:0; top:0;padding:10px;z-index:1000;text-align:center;';

      var cookieConsentElement = document.createElement('div');
      cookieConsentElement.id = cookieConsentId;
      cookieConsentElement.style.cssText = butterBarStyles;
      cookieConsentElement.appendChild(_createConsentText(cookieText));

      if (!!linkText && !!linkHref) {
        cookieConsentElement.appendChild(_createInformationLink(linkText, linkHref));
      }
      cookieConsentElement.appendChild(_createDismissLink(dismissText));
      return cookieConsentElement;
    }

    function _createDialogElement(cookieText, dismissText, linkText, linkHref) {
      var glassStyle = 'position:fixed;width:100%;height:100%;z-index:999;' +
          'top:0;left:0;opacity:0.5;filter:alpha(opacity=50);' +
          'background-color:#ccc;';
      var dialogStyle = 'z-index:1000;position:fixed;left:50%;top:50%';
      var contentStyle = 'position:relative;left:-50%;margin-top:-25%;' +
          'background-color:#fff;padding:20px;box-shadow:4px 4px 25px #888;';

      var cookieConsentElement = document.createElement('div');
      cookieConsentElement.id = cookieConsentId;

      var glassPanel = document.createElement('div');
      glassPanel.style.cssText = glassStyle;

      var content = document.createElement('div');
      content.style.cssText = contentStyle;

      var dialog = document.createElement('div');
      dialog.style.cssText = dialogStyle;

      var dismissLink = _createDismissLink(dismissText);
      dismissLink.style.display = 'block';
      dismissLink.style.textAlign = 'right';
      dismissLink.style.marginTop = '8px';


      content.appendChild(_createConsentText(cookieText));
      if (!!linkText && !!linkHref) {
        content.appendChild(_createInformationLink(linkText, linkHref));
      }
      content.appendChild(dismissLink);
      dialog.appendChild(content);
      cookieConsentElement.appendChild(glassPanel);
      cookieConsentElement.appendChild(dialog);
      return cookieConsentElement;
    }

    function _setElementText(element, text) {
      if (supportsTextContent) {
        element.textContent = text;
      } else {
        element.innerText = text;
      }
    }

    function _createConsentText(cookieText) {
      var consentText = document.createElement('span');
      _setElementText(consentText, cookieText);
      return consentText;
    }

    function _createDismissLink(dismissText) {
      var dismissLink = document.createElement('button');
      _setElementText(dismissLink, dismissText);
      dismissLink.id = dismissLinkId;
      dismissLink.style.textDecoration= 'none';
      dismissLink.style.color= '#666';
      dismissLink.href = '#';
      dismissLink.style.marginLeft = '24px';
      return dismissLink;
    }

    function _createInformationLink(linkText, linkHref) {
      var infoLink = document.createElement('a');
      _setElementText(infoLink, linkText);
      infoLink.href = linkHref;
      infoLink.target = '_blank';
      infoLink.style.textDecoration= 'none';
      infoLink.style.color= '#33CC33';
      infoLink.style.marginLeft = '8px';
      return infoLink;
    }

    function _dismissLinkClick() {
      _saveUserPreference();
      _removeCookieConsent();
      return false;
    }

    function _showCookieConsent(cookieText, dismissText, linkText, linkHref, isDialog) {
      if (_shouldDisplayConsent()) {
        _removeCookieConsent();
        var consentElement = (isDialog) ?
            _createDialogElement(cookieText, dismissText, linkText, linkHref) :
            _createHeaderElement(cookieText, dismissText, linkText, linkHref);
        var fragment = document.createDocumentFragment();
        fragment.appendChild(consentElement);
        document.body.appendChild(fragment.cloneNode(true));
        document.getElementById(dismissLinkId).onclick = _dismissLinkClick;
      }
    }

    function showCookieConsentBar(cookieText, dismissText, linkText, linkHref) {
      _showCookieConsent(cookieText, dismissText, linkText, linkHref, false);
    }

    function showCookieConsentDialog(cookieText, dismissText, linkText, linkHref) {
      _showCookieConsent(cookieText, dismissText, linkText, linkHref, true);
    }

    function _removeCookieConsent() {
      var cookieChoiceElement = document.getElementById(cookieConsentId);
      if (cookieChoiceElement != null) {
        cookieChoiceElement.parentNode.removeChild(cookieChoiceElement);
      }
    }

    function _saveUserPreference() {
      // Set the cookie expiry 31 days after today.
      var expiryDate = new Date();
      expiryDate.setDate(expiryDate.getDate() + 31);
      document.cookie = cookieName + '=y; expires=' + expiryDate.toGMTString() +'; Path=/;';
    }

    function _shouldDisplayConsent() {
      // Display the header only if the cookie has not been set.
      return !document.cookie.match(new RegExp(cookieName + '=([^;]+)'));
    }

    var exports = {};
    exports.showCookieConsentBar = showCookieConsentBar;
    exports.showCookieConsentDialog = showCookieConsentDialog;
    return exports;
  })();

  window.cookieChoices = cookieChoices;
  return cookieChoices;
})(this);

function delete_cookie(cookie_name)
{
  var cookie_date = new Date ( );  
  cookie_date.setTime ( cookie_date.getTime() - 1 );
  document.cookie = cookie_name + '=; Path=/; expires=' + cookie_date.toGMTString();
}

<a href="#" onclick="delete_cookie('displayCookieConsent');" class="">clicca qui per cancellarlo</a>

ps. sto lavorando sul sito in locale, può centrare qualcosa?

Grazie in anticipo