In all fairness, most who say those things are ex-Catholic themselves, so you can't really call them ignorant. They simply look upon their upbringing differently than you do.
Frankly, I find former Catholics to be the most ignorant of the real teachings of Catholicism, and, as you noted, the most offensive. If they knew the faith, they would not have left it. Of course, a large percentage, a majority in my experience, are "emotional," not "intellectual" converts.
Emotional converts are the divorced & remarried, the "Father So-and-so was mean to my dad," "Sister Such-and-such hit my knuckles with a ruler," and those easily swayed by the emotionalism and feel-good-ism of the simplistic false gospels out there since 1517.
Few are truly "intellectual" converts. Few leave the Church after having honestly studied the faith, the teachings of the early Christians, and the historical interpretation of scripture. The honest intellectual conversions by and large go through a one way door, into sacramental Christianity. When you talk to the rest long enough, you find the hurt or the insult or the other emotional aspect that precipitated the conversion. You also find that by offering a resolution to that emotional trauma, you can readily bring them home to Rome.