Discrimination by class is definitely not a morally sensitive issue nowadays the way sex or race is. On the contrary, success in life is nowadays measured mostly by one's ability to distance and insulate oneself from the lower classes
Without disagreeing much with your comment, I have to point out that this is a non sequitur. Moral sensitivity has nothing to do with (ordinary) actions. Among countries where the second sentence is true, there are both ones where the first is true and ones where the first is false. I don't know so much about countries where the second sentence is false.
As to religion, in places where people care about it enough to discriminate, changing it will probably alienate one's family, so it is very costly to change, although technically possible. Also, in many places, religion is a codeword for ethnic groups, so it can't be changed (eg, Catholics in US 1850-1950).
You're right that my comment was imprecise, in that I didn't specify to which societies it applies. I had in mind the modern Western societies, and especially the English-speaking countries. In other places, things can indeed be very different with regards to all the mentioned issues.
However, regarding your comment:
Moral sensitivity has nothing to do with (ordinary) actions.
That's not really true. People are indeed apt to enthusiastically extol moral principles in the abstract while at the same them violating them whenever compliance would be too cos...
A few examples (in approximately increasing order of controversy):
If you proceed anyway...