You quoted:
"The necessaries of life occasion the great expense of the poor. They find it difficult to get food, and the greater part of their little revenue is spent in getting it. The luxuries and vanities of life occasion the principal expense of the rich, and a magnificent house embellishes and sets off to the best advantage all the other luxuries and vanities which they possess. A tax upon house-rents, therefore, would in general fall heaviest upon the rich; and in this sort of inequality there would not, perhaps, be anything very unreasonable. It is not very unreasonable that the rich should contribute to the public expense, not only in proportion to their revenue, but something more than in that proportion"
Adam Smith is NOT talking about income taxes here. He is talking about property taxes. He said that since the rich own more and better property it is only fair that they pay more for their house than a poor man. How that relates to a progressive income tax takes quite a stretch. He says that the rich should pay in proportion to their revenue (income tax) and a higher proportion on their property tax. You are stretching that to say "pay a higher proportion on income tax and a higher proportion on property tax".
If one looks closer, one sees that he does not endorse a higher proportion on the rich, he just notes that a property tax would fall higher on the rich and then says it would be unreasonable, but PERHAPS it wouldn't be VERY unreasonable.
Also, I liked the way you said that you think Adam Smith's ideas are mostly wrong but you are going to cherry pick the few that can be twisted to agree with you. A lot of intellectual honesty there.