I personally see nothing wrong with being taught to be modest in public. I also see no conflict in being modest in public and sexual with your wife/husband. I think the idea that the sexual part of you is saved only for your spouse is good for a marriage. Many religions teach that you should be modest in public and wait until marriage for sex, and that sex within marriage is a wonderful and bonding experience.
The Duggars have never said that sex is only for procreation and I seriously doubt they will stop having sex when Michelle can't get pregnant anymore. She appears to me to be a very strong woman with a mind of her own and I have never seen Jim Bob treat her as anything less. In fact I cannot imagine him talking her into anything she didn't want to do, much less getting pregnant when she didn't want to or not getting pregnant when she did.
They treat other people with respect and have no problem having cousin Amy as part of their lives and around their children, even though she doesn't live in the same way they do and even criticizes their choices.
I think sometimes anger about our upbringing can cloud our judgment and make us all the more judgemental. Bad things happen in all kinds of families and all kinds of religions. There are millions of happy Catholic, LDS, Baptist and other religious families, that doesn't mean they are all good. There are millions of unhappy religious families as well, that doesn't mean they are all bad. Small families, big families, atheist families, religious families, they all have good and bad families.
Painting with a broad brush saying all religious families or all large families are this way or that way is disingenious. I think we need to be careful here to not put our own preconceptions onto this family.