[mancerayder]

That's a clear straw man argument, that there exists a sequence of events between people buying stocks on margin, going bankrupt, and living off of government assistance. And this occurrence is so commonplace as to warrant a proposed punitive tax on margin trade profit? What evidence do you have that this actually happens? I think you ARE making a moral argument, namely around 'risk taking' being something that society should punish and discourage via taxation. You left the second part, the societal cost (which may be real, who knows, you only offered a hypothetical government assistance scenario) completely in the realm of speculative fancy.

Not to mention, if you really truly wanted to morally punish and discourage gambling, I seriously doubt a tax on profit would make a dent in it! Have you ever met a real gambler?