[Symmetry]

If a consumer is conscientious enough to recycle something, the counterfactual is that they put it in the trash rather than that they throw it into the nearest river. In a landfill, a plastic bottle will lock up its constituent carbon for hundreds of years. In that long we should either have learned to manage the amount of carbon in our biosphere. To the extent that the amount of carbon we pump out of the ground is inelastic, better it get locked up in landfills than that it get burned. Now actually it is fairly elastic but given how much worse carbon burned is than carbon stored for hundreds of years I think disposal is probably better for the climate than recycling.

[fluoridation]

I seem to recall that something 10% of the oil that's extracted is used to make plastics, while the rest is used for energy. Framed that way, it could be argued that it doesn't make much of a difference if it gets burned (especially if it's burned in lieu of burning some other fuel), but if it's burned there's no chance it will pollute a river or ocean.