One should be able to put code for both removing listeners and adding the CSS override into a bookmarked. That will not trigger the anti-debugging crap.
javascript:(function(){var style=document.createElement('style');style.type='text/css';style.innerHTML='* { user-select: all !important; }';document.head.appendChild(style);document.body.oncontextmenu=function(){return true;};})();
(Untested)
Superfluous. I don’t understand why people often do this on stylesheets or scripts (type="text/javascript"), because it has never at any time been necessary or useful.