I suspect you got it backwards here - the plastic you use in a year does much, much deeper damage than emissions from a flight. But in the end these different types of environmental issues are not exclusive. You can reduce your plastic consumption and plane travel!
Much of the plastic in the great garbage patches are fishing related. And the countries where there are laws regarding plastic bags are not the ones dumping them in the ocean. That's mostly the "developing world" (pardon that phrase, can't think of a less awful one). They're clearly not going to adopt "vegan spider silk" bags or any other "greener" alternative; they don't have the money.
> the plastic you use in a year does much, much deeper damage than emissions from a flight
Nah. ~100% of the single-use plastics I use are incinerated and most of the embodied energy is recovered. I would say 100%, but I can't rule out a garbage truck crashing and losing a bit of cargo or sometihng.
Environmentalism is full of these pointless "little things" which people think add up to "a big thing", but don't. Tin foil. Cling film. Plastic bags. Paper towels. These are all convenient in daily life and insignificant in the grand scheme of things. This seriously detracts from the message of real environmentalism.
It's much easier to wag a finger at someone and tell them "you mustn't use plastic bags, they're bad for the environment!" than it is to tell them "don't go on vacation to Hawaii, flying is criminally wasteful".