Its not realistic to get enough people voluntarily stop to destroy the planet, it is however feasible to get a government changing its policies to alter the structures that incentivize pollution.
People don't need meat.
> clothes
People don't need leather goods or slave labor or fashion brands.
> transport
People don't need SUVs or Corvettes.
> optimizing for good is a complex problem
This is not a complex calculation: in all cases they're more expensive, worse for you, and worse for the world than readily available alternatives. And yet here we are, because, just like drugs, they're fun.
- Balancing your family's diet without meat requires specialist knowledge and effort that "not buying drugs" does not.
- Balancing your family's transportation needs with environmental friendliness requires specialist knowledge (chiefly the carbon impact associated with different candidate vehicles) and additional cost (an environmentally friendly vehicle with equivalent capacity is almost always going to cost more) which is also not true for "not buying drugs".
- Assessing every candidate clothing item's working conditions requires lots of specialist knowledge and effort that isn't true for "not buying drugs".
And this is without comparing the marginal impact of an individual's environmentally inefficient consumer choices to a drug user's significant and direct impact on drug violence. You'd have to place a pretty low price on human life (especially the minority communities that are most impacted by drug violence) to make this equivalency.