We feel apologetic about the differences in Hindu society especially since we think that the followers of other religions are not divided in the same way as we are. The latter are scornful of Hinduism on this score and some Hindus themselves feel that the differences in our society are unjust. But, if you pause to reflect on the subject, you will realise that if our civilization has survived from prehistoric times until today it is only because of these very differences in our society, the differences according to varna dharma.
In other religions too, even if there is no caste according to their scriptures, the communities are divided. Some of the divisions are almost like jatis and they do not intermarry. Muslims are divided into Sias (Shias), Sunnis and Ahmadiyas. In the south the Pattanis (Pathans) and Labbai Muslims do not intermarry. Among Christians there are Catholics, Protestants and followers of the (Greek) Orthodox Church. Hindus are divided on the basis of labour or work, but are united on another level. But followers of other religions, though themselves divided, speak ill of us. Yet we do not respond properly to their criticism.
For a general background, please see here