I think that Tom is shown to be a bad husband as a bad person in a variety of ways. Tom's physical force or strength is the primary means of communication. It is this brute sense of character that makes him such a bad husband in that he believes that rules and norms of ethical conduct do not apply to him. It is for this reason that he is able to step outside of his marriage with so much of a brazen mentality. The fact that he mistreats his wife is seen in how he treats people in general. George Wilson gets no respect from Tom and Myrtle is nothing more than a "keep" for Tom. The manner in which he savagely beats her in front of others is reflective of how disrespectful he is to women. Even when he is with Daisy, he does not do much to care for her. He looks at her as no more than a trapping of his wealth, an object that must be kept for his own sense of possession. In this, he is a terrible husband. Fitzgerald makes it very clear that Tom's poor character is what ends up making him both a lousy husband and an as bad human being.