This poll is quite poorly set up.
The question is not whether or not we should take healthcare away from a group, but if we should give healthcare to a specific group, which gives the impression that this is some unieque previledge that is bestowed upon the group as a reward for their activities.
Anyway no, we should not discriminate.
If the goal is to enhance public health then raising taxes and in other ways inhibit the unhealthy businesses from expanding their consumer base.
If the goal is to save money then for this question to be posed, Australia must be bankrupt in it's finances, morals or wits. If you start confiscating people's rights based on your dislike of their habits then the course is set towards a nannystate at best. If you start excluding expensive illnesses then you are not going to have trustworthy public healthcare for long. If you have to do the former, then perhaps it's time to review whether public healthcare is even possible when finances are in such dire straits.
On the subject of smoking and unhealthy food, raise taxes on them, and lower it on healthy food and services that are beneficial to public health. Make it attractive and affordable to be healthy while ramping up the cost of an unhealthy lifestyle and the state will have done it's part without stepping on the rights of the individual.