Well, as the cost can dissuade people from doing virtuous things, as we programmers well know, it should follow that such costs would be partly effective to dissuade people from doing bad things.

Particularly if they're not so high as to effect a "ban", the effect is a ban on people less affluent than some mark making "sinful" purchases in a particular jurisdiction. Sin taxes are particularly regressive, since they tend to be higher than typical sales taxes (which are already regressive in some sense).

If policy makers are concerned about potential regressive effects, they could take the revenue earned and apply it towards helping the poor. One "easy" method is lowering the bottom tax bracket - in the US they could cut the explicitly regressive payroll tax.

Social security (the large majority of the payroll tax) is highly progressive when paid out and then taxed.

This isn't a critique of social security payouts -- other than political expediency, there is no particular need to couple the payments with the current payroll tax source.

The end result is still a policy which oppresses the people who can not afford the tax more severely than it oppresses those who can. If the desired effect is a reduction in smoking, for example, the appropriate approach is to track and limit sales on a per-person basis. This, of course, is less attractive to the state, and more cumbersome to administer and specify, but it doesn't suffer from the obvious moral wrong: artificially pricing people out of perceived vice on the basis of class.