The whole point of nationalized healthcare is to make sure that the populace receives the care that they need but which they cannot afford. Taxing the holy hell out of people because they choose a lifestyle - a legal one - that is not popular is essentially coercing those people to make the 'correct' choices despite being within their legal rights to choose otherwise. It's racketeering: you make the choices I want you to make or you pay the hefty price.
If cigarettes place an undue burden on the healthcare system (or on society), then gather the oomph to make them illegal. If alcohol does the same, gather the support to make it illegal. (Oh, wait, we tried that. How'd that turn out, again?) It's the same with any drug, any poison, any leisure activity. Is there a skydiving tax? "Bad example," you say, "because skydivers are supposed to use parachutes and not die." Okay, then - what about a failed-suicide tax? If someone tried to kill themselves and failed, they have made personal choices that place an avoidable burden on the healthcare system. But it's almost unthinkable to tax someone like that.
It's not a case of "Well, I'm trying to keep an eye out for the healthcare system". It's "Well, I don't think this is acceptable, and I don't want my tax dollars going for this, so clearly this person should pay a whole lot of taxes to assuage my indignation over it". And that is wrong.
Edit: It's been kindly pointed out to me that I've gotten off on a bit of a tangent, which I didn't mean to do. Gonna bow out now, with my apologies. ^^