You are referring here to the part where the three women come over to hang out with Millie and Guy tries to get them to talk. I think that Bradbury picks these three topics because they are all traditional things that people would talk about in our day.
In our day, it would be quite usual for women to talk about their kids and pretty usual for men or women to talk politics and war. But with these three, none of the subjects really interest them. They do not care about any of it.
So this is showing that people in the book do not care about any of the things that we think are important.
My colleague above is right, of course. None of the women (Mildred, Mrs. Phelps, Mrs. Bowles) show any true interest in the subjects they happen to be discussing. In fact, Bradbury shows how superficial and shallow the women are through their conversation. The women have essentially allowed their minds to be brainwashed by prolonged exposure to systematic, government-sponsored programming; their media habits have left them little opportunity to develop sustained interest in anything meaningful.
While discussing war, the women display an utter lack of understanding about the true nature of warfare. Mrs. Phelps proclaims that her husband, Pete, has just been called to battle. However, she professes to be utterly unconcerned about his safety, as the Army has supposedly assured her husband that it will only be a "Quick war." She reiterates at least four times that she is not worried about the ramifications of such a conflict. The other two women concur, noting callously that "It's always someone else's husband dies, they say." The women display a disturbing naivete borne out of ignorance. It never occurs to any of them to question the necessity of such a war; they accept what they are told without reservations.
As Montag desperately tries to engage the women in meaningful discourse, they rebel at his efforts to draw them out. In concert, all the women agree that the subject of children is distasteful. They are oblivious to the effect their obnoxious attitudes have on Montag. Mrs. Phelps adamantly proclaims that "children are ruinous" while Mrs. Bowles revels in the knowledge that she can give as good as she gets when it comes to physical altercations between her and her children.
The women don't fare much better when it comes to the subject of politics. All of them agree that President Noble is a good leader because he is photogenic, tall, and charismatic. They spend some time castigating Noble's political opponent, Hubert Hoag, for being short, homely, and lacking in style. Meanwhile, Montag is utterly disgusted that the women have chosen style over substance in their evaluation of presidential candidates. So, Bradbury uses the conversational element as a literary device to highlight the insidious effects of continuous exposure to ceaseless media programming. The women lack discretion, judgment, and self-awareness. The daily obsession with media has left little time for contemplation and deep analysis. Furthermore, the war against books and substantive knowledge has added to the women's intellectual paralysis.