I also don't think people know what a plot hole really is.
A plot hole is a gap or inconsistency in a storyline that goes against the flow of logic established by the story's plot, or constitutes a blatant omission of relevant information regarding the plot. These include such things as unlikely behavior or actions of characters, illogical or impossible events, events happening for no apparent reason, or statements/events that contradict earlier events in the storyline.
While many stories have unanswered questions, unlikely events or chance occurrences, a plot hole is one that is essential to the story's outcome. Plot holes are usually seen as weaknesses or flaws in a story, and writers usually try to avoid them to make their stories seem as realistic as possible.
So, Alpha being sane and a good guy IS essential to the story's outcome. And there's no rhyme or reason for him being sane. He just was. Just a line or two would clear that up. It's unlikely behavior for Alpha, and it's an impossible event, by the perimeters of the story.