Papa is definitely not the guy you want your daughter, sister, or friend to marry—even before he becomes a total lush, he's got the personality of an irresponsible, arrogant, insecure boy. Let's just say Mama's parents "were terrified when they saw him coming. He not only led what seemed to them a perilously fast life; he also borrowed money" (1.5.14). Ha.
And he does turn out to be completely unstable. Before becoming a fisherman, he goes from job to job—lumberjacking, dentistry, farming. And let's not forget that before he meets Mama, he's a law school student (who then quits for unknown reasons).
And then, of course, there's his behavior both during and post-camp life. He's clearly unable to deal with the emasculation that comes with not just internment, but all the rumors about him being an inu or collaborator:
It was the charge of disloyalty. For a man raised in Japan, there was no greater disgrace. And it was the humiliation. It brought him face to face with his own vulnerability, his own powerlessness. He had no rights, no home, no control over his own life. (1.9.1)
No wonder the man drinks like a fish once he gets to Manzanar. Who can blame him?
But still—all that psychological baggage doesn't really excuse how awful he is to his family, does it? As Jeanne points out, the whole experience of living with him is like a whole different kind of hell:
He kept pursuing oblivion through drink, he kept abusing Mama, and there seemed to be no way out of it for anyone. You couldn't even run. (1.8.23)
What kind of man deals with his life like that?
The kind of man who thinks he's the Man (yes, capitalized), the person everyone else should be bowing down to. After all, what do you expect from the oldest son of a samurai family, a "headstrong idealist," "spoiled, the way eldest sons usually are in Japan, used to having his way" (1.6.5)?
With this in mind, it's really no surprise that he's all about being the domineering patriarch who blames his wife for his own actions:
"I can never go outside, because of you!" he screams at Mama, even though she clearly has nothing to do with the fact that he's a total shut-in when he arrives at Manzanar. (1.8.14)
Nor is it much of a shock that he wants Jeanne to be a traditional Japanese girl who thinks "[m]odesty is important," "[a] graceful body is important"—a girl who "[doesn't] show [her] legs all the time" (2.21.29). Someone, in other words, who can marry a Japanese boy instead of some hakajin (white) boy.
No doubt about it: Papa's your classic macho man who can't take being seen as anything other than a macho man.
But his total drive to be the man in control is also what inspires Jeanne to let go of her fear of the outside world and its racism toward Japanese-Americans. When he drives like a maniac back to Los Angeles, Jeanne is "almost ready to laugh with him, with the first bubbly sense of liberation his defiant craziness [brings] along with it. [She believes] in him completely just then, believe[s] in the fierceness flashing in his wild eyes. Somehow that [will] get [them] past whatever wait[s] inside the fearful dark cloud" (3.1.52).
Think of Papa as a jerk without a cause… but give him a cause and he becomes a little less of a jerk.