Although hate speech is never acceptable, much of what is classified as "politically incorrect" does not qualify as hate speech. Hate speech is "a legally actionable attack on a particular group provoking hatred."
Politically incorrect statements aren't necessarily intended to be an attack to provoke a certain response. Instead, it is often based on ignorance of "correct labels."
Further, people are often characterized as "politically incorrect" for sharing opinions that are not offensive to vulnerable people groups, they are simply unpopular. We cannot defend political correctness through saying that it prevents hate speech, because much of what is classified as politically incorrect is not pervaded by racist, sexist, homophobic, or transphobic sentiments. Rather, politically incorrect statements are merely unpopular, not hateful, ways of speaking.