What must I do to atone for describing some girls as irreligious and ignorant in matters of faith, given my feeling of guilt out of fear that they will be alienated from religion because of me, and is my statement that a woman's work in her home is preferable to her working outside it correct?

If the situation is as you described, it does not appear that you are sinful for describing these women as having weak religious commitment and ignorance of the religion, especially if they mocked you; this is based on the statement of Sheikh al-Islam Ibn Taymiyyah: "So, whenever the addressed person has committed injustice, we are not commanded to respond to him with that which is better." It is preferable to avoid engaging in arguments with such women and to be keen on using good words. If you wish to be cautious, seek forgiveness from Allah and repent to Him, and soften your speech towards them to win over their hearts and help them accept the truth.