Isn't discrimination based on race, gender, sexuality and otherwise inherently spooked? The concepts of race and gender and such are themselves geists too.
Stirner isn't universally accepted by the left wing. Most Marxist-Leninists dislike him and deem him bourgeoisie, while anarchists are split on the issue, some rejecting him altogether in spite of his real influence on individuals such as Emma Goldman.
Most of what has been labeled "the left" - particularly the Marxist-Leninists and such - are haunted by fixed ideas such as "the revolution" or "the worker's state". Marx himself hated Stirner and wrote a lot in an attempt to debunk Stirner's writings because they were anathema to Marx's own.