The Almighty Allah has decided and announced in the Qur'an that the whole mankind is a single nation. The Almighty further says that it is only Mushriks (polytheists) who are bad. He also explains that lowly and illegitimate are those who are disobedient and haughty. In spite of all this clarification whole of the Muslim society is going against the decision of the Almighty. They term many human beings as "kamīn" (lowly). They do not allow them to be known with their tribe name. We have therefore in our society classes of people like blacksmiths, carpenters etc. We refer to the people by these names derogatively. Isn't it following Hindu caste system? This situation becomes more terrible when we see that not even a single sect, scholar or religious party notices this issue. I think all the sects like Shia, Brelvi, Ahl-e-hadith, Dew-bandi etc. are unanimous on this base custom.
I believe you are very clear on the teachings of the Qur'an on the subject. You are also clear on the moral stance in this regard. However, I believe scholars of all sects hold that it is unjust to consider someone lowly on the basis of their caste or profession. All the scholars from all the sects hold that it is only taqwa that is measure of eminence and excellence.
However, they do not engage in active efforts to teach the people to observe the Qur'anic injunctions in this regard and observe these themselves. It is not only a sin but a crime for it directly affects the opportunities they have in the society to progress. It is the duty of all the scholars to address this issue and come forward to lead the community out of this darkness of ignorance and sin.
A lot of efforts and gradual teaching is required if this issue is to be address properly. This is because it is rooted deep down in our social values and mental attitudes. We cannot dig this out in a single stroke. It may take generations to curb this evil but we must start playing our role in this direction if we have to face the Lord Almighty on the last day and present our excuse saying that we did our best