What exactly is a protagonist?

I don't know if you're like me, but I hate the question, "so, who's the good guy in this movie?" It's a benign enough question, but I feel that placing characters in a "good or bad" binary robs us of the tools to have a nuanced discussion about narrative. Take Breaking Bad, and the visceral/misogynistic response certain toxic segments of the fanbase had to Skyler White.

Because millions of viewers chose to view Walter White as the "good guy" in Breaking Bad, any character that slightly impeded his ascension to the apex of the meth world was vilified by the fandom as a "bad guy." Consequently, Skyler White- a pregnant, 40-year-old mother of a teenage disabled son- became one of the most hated characters in television for simply wanting her murderous, drug-dealing, lung cancer-ridden husband to stop lying to her. Now, if we just call Walter White a villainous protagonist instead of a "good guy," we can easily rectify the fandom's collective misapprehension. Probably not, but, hey, I can dream, can't I? 

In the video linked above, the YouTube channel Studio Binder explains the different types of protagonists in fiction.