It's quite reactionary to label betting as addiction markets. I see little reason to draw that corollary to other, often detested, vices.
To label such activity as a tax on the poor is nothing more than a euphemism. I understand what is being said by the verbiage "tax" in this context. Although no real tax is voluntary.
Labeling this as an issue that disproportionately affects poor is misleading. This is an issue for a few select individuals who make poor decisions. The correlation for poor decisions and lower disposable income is higher than the contrary.
Wealthy by all means have the ability to wager more than they can afford. Often times, they wager significantly higher than average income individuals; however, they stay within their means