I have to disagree with you sanctus... I don't think they necessarily knew the reaction they'd recieve. Many Catholics I know go through the motions without questioning what's behind what they're doing. They don't stop to think about what they're reciting, what they're promising, what's expected of them. If you've gone to mass all your life, gotten up, walked to the front, taken the wafer, and nothing has changed for you, then why would you think you still couldn't? I guarantee you these women don't feel immensely different than they did as children, they don't feel that they have gravely changed somehow. To them, mass is what it always has been, and they are who they always have been, so why expect such a reaction, if you haven't thoroughly thought it through?
In most cases I'd agree with you, but not in this case. No matter what, these ladies must know that the Church does not accept homosexual "weddings" as valid.
Though in most other things you're surely correct, most people have no idea why they are doing most of the things we do at Mass.