You will rarely hear a whom in informal (General North American) English, thought it occasionally occurs in examples like these - after a preposition. We prefer the unmarked who in most cases. There's no 'should' about it - it's just what comes naturally, as Warsaw Will said.
The case marking rule for who/whom applies to formal/edited English, in which case your editor or proofreader would probably suggest changing some of these to whom. But a scriptwriter would want to make his or her characters sound natural and informal for the most part. Movies are a good place to learn about the grammar of spoken informal to semi-formal English.
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