Okay, so imagine you just ban plastic soda bottles. Now plastic bottles cannot be used in any circumstances, no matter how genuinely warranted, even if a user is willing to pay all costs to ensure its environmental impacts are offset. Also, all soda is now significantly more expensive, so “the poors” still have less access to it.
And by definition the amount you would have to tax to achieve this has to be so much that it destabilizes the market.
Potentially, yes. The entire point is that these artificial low prices are only possible because the negative externalities are being inflicted on other people in the form of pollution. By actually factoring this impact into the cost of the good, its true cost emerges and the market will settle into whatever the equilibrium is. If the only thing enabling mass access to cheap soda is a ton of pollution, then you either accept mass pollution or you lose the mass access to cheap soda. There’s not really any way around that fundamental trade-off.
Well, this is Brown we’re talking about. The students probably got too high and just accepted whatever deal was thrown at them without thinking about it.