Why should it be comparable to tobacco? It should be derived from first principles. Figure out the external cost to society and tax it enough to pay for those costs after money distribution overheads. If there is no tax structure where the revenues exceed the costs, ban it.

The difficulty with taxing prediction markets is that encouraging gambling on some events incentivizes gamblers to try to influence those events in a way contrary to how people would want to influence them in the absence of gambling, which typically means gamblers are incentivized to influence events in a way that will increase societal harms. For some events, resolving one way or the other is inconsequential, but this is not true for many of the events I see people gambling on in prediction markets.