so-called "sin taxes" are morally neutral but economically efficient. Explanation: one of the problems with taxation is that taxes distort the economy by changing prices which change consumption; "sin goods" have inelastic demand functions--smokers still want their cigarettes--so taxation doesn't change consumption, which lessens side effects of the taxation, for example not increasing unemployment of cigarette workers.

They can also be popular with the electorate ("first they came for the smokers, and I didn't complain because I was not a smoker..") because people make moral judgments which is what you are complaining about, but that's not the reason economists favor them when it comes to advising politicians on tax policy.