There are a couple of ways that critics view the marriages in the play. One view is to see the marriages as a way for the men to reassert their control over females. Others see the marriages as a way of restoring balance between the sexes.
There is no doubt that a double standard exists for men and women in society, especially regarding sex outside of wedlock. If a man and woman engaged in sex before marriage, it was blamed on the woman, who was seen as the villain in such a tryst. The man could never be blamed for the seductive powers of a woman.
Chastity was also important to any man considering marriage to a woman. No man wanted to marry a woman who had not remained a virgin. When Lucio is sentenced to marry any woman who comes forth and says he impregnated her, Lucio sees this as bad as "pressing to death, whipping and hanging". For Isabella, her chastity is not negotiable. Her moral standards are absolute, and she's angered that Claudio would dare ask her to even consider giving up her virginity in order to save his life.
The Duke also views the sentences of Claudio, Angelo, and Lucio as proper punishments for their behavior. It's not that the Duke is angry for what's happened to the women; it's more that he views the men as hypocritical and improper. Claudio got Juliet pregnant, and Lucio has impregnated no telling how many women. The Duke's anger at Angelo is his reason for Angelo's marriage to Mariana.