On the surface, it might seem right to condemn Mrs. Hale and Mrs. Peters for obstructing justice. After all, the two women suppress a crucial piece of evidence that offers a motive for Mrs. Wright to have killed her husband. That evidence is the bird, carefully wrapped and saved, that Mr. Wright killed in a fit of rage. The women realize that this killing of a beloved pet caused Minnie to snap and kill her husband.
One might wonder why the women withhold the evidence. However, the men's highhanded and patronizing attitude towards Mrs. Hale, Mrs. Peters, and Minnie Wright shows that they don't understand a woman's world. The men look down on woman's work as trifling. They miss crucial evidence that would have helped them solve the case because they are too arrogant to see that women's domestic lives are important.
As the play unfolds, the subtext unfolds as well. Mrs. Hale and Mrs. Peters realize that the normalization of male violence towards women, be it through belittlement or hacking a girl's kitten to death, means they have to protect Minnie Wright. She is unlikely to be understood or to get a fair trial from a legal system run by males. By the end of the play, we understand why the women believe John Wright's death was a justifiable homicide and why they hide the evidence.