If Article I, Section 8 of the Constitution has, in fact, been debunked, I am not aware of it. The general welfare clause is, in fact, a recognition of the duty of the government to protect its citizens against those who would do them harm.
Given that, if this is a valid exercise of the Commerce Power within it's intended purpose there should be some manner of injustice that the existence of e-cigarettes has or will cause to be visited on one state by another, which banning them will remedy or prevent.
Regulating is not banning. Regulating means that manufacturers have to comply with health, quality, and safety standards. People buying e-cigs should not be subjected to, for example, the devices exploding and blinding them because they were badly engineered and made with poor-quality components.
E-cigs are sold across state and international borders, which places regulating them in the purview of the federal government, rather than state governments.
There are many problems with the libertarian view that the FDA should be abolished. One of them is the belief that the market can somehow guarantee product safety through the actions of injured customers suing manufacturers of faulty products. Why wait until injuries occur? Why not make sure the product conforms to standards so that people do *not* get hurt? Another is the implied belief that doing away with the FDA would stop product regulations. It would not. The states would take over that function, and then regulations would be all over the place, ranging from so strict that almost nothing can meet the standards, to so lax that they almost don't exist. Or the standards in one state could contradict the standards in another. The burden on manufacturers to make products that comply with 50 different regulatory standards would be huge, and many manufacturers could decide not to sell in certain states because of the costs associated with conforming to their standards.
In case you missed it: Regulation is not banning. Regulation is about making sure products meet certain safety and quality standards.
James Madison, from Federalist 83
"If Congress can employ money indefinitely to the general welfare, and are the sole judges of the general welfare, they may take the care of religion in to their own hands; they may appoint teachers in every State, county, and parish and pay them out of the public treasury; they may take into their own hands the education of children, establishing in like manner schools throughout the Union; they may assume the provision of the poor . . . Were the power of Congress to be established in the latitude contended for, it would subvert the very foundations, and transmute the very nature of the limited government established by the people of America."
It doesn't go unnoticed the ingenuous tactic of changing debunking the notion of the general Welfare clause being a grant of power to debunking Article I Section 8 in it's entirety.
As far as it being a regulation rather than a ban, it's effectively the same thing if it puts all of the manufacturers out of business.
Excusing this is just going to invite more of the same until they exercise absolute control over every single facet of your life.