I agree in general, but it makes the analysis more complicated, I think, especially when considering marginal usage/activity from the perspective of an end user/consumer.
For example, one could naively believe that there's absolutely no marginal emission from deciding to get on a plane. The plane is emitting basically the same amount whether there's 99 people on board or 99 + 1 (you) on board, and the plane's going to make that particular flight whether or not you get on. However, you're funding the airline industry and increasing demand (and therefore supply) for flights along that route and perhaps also indirectly helping pay for other things the airline is doing, so that could probably be considered a marginal emission contribution.
If you ignore transaction fees for a moment, it seems like this logic doesn't quite work for cryptocurrency networks. It seems like a closer analogy would be something like a contrived scenario with an airline that has routes which are absolutely static and predetermined (e.g. a contrived scenario where an airline decides it's going to fly a passenger plane a certain route once per day every day at the exact same time for a year no matter what, even if no one's aboard, and also the tickets are free if assuming no transaction fees). There are still the indirect issues with supporting the network, but it seems like there's less of a marginal emission concern if you're someone who's just making transactions, or arguably even no marginal emission concern.
In reality, you are adding some marginal emissions due to transaction fees (direct incentive to mine), and the indirect incentives could maybe be broken down into something marginal as well (no one using the network = no incentive to mine since the currency would probably have no value), but basically it kind of feels like there's less of a direct marginal emission concern as an end user of the network compared to something like getting on a plane, especially if you take transaction fees out of the equation. In that sense, it feels like abstaining is somewhat more of a moral protest rather than a direct economic "vote" or boycott.
Am I wrong about any of this? I probably am; this is just a random thought. Maybe the transaction fees are the crux of it (even if the block rewards are much more lucrative), so eliminating them from the equation for the sake of argument makes the whole point moot?
For example, one could naively believe that there's absolutely no marginal emission from deciding to get on a plane. The plane is emitting basically the same amount whether there's 99 people on board or 99 + 1 (you) on board, and the plane's going to make that particular flight whether or not you get on. However, you're funding the airline industry and increasing demand (and therefore supply) for flights along that route and perhaps also indirectly helping pay for other things the airline is doing, so that could probably be considered a marginal emission contribution.
If you ignore transaction fees for a moment, it seems like this logic doesn't quite work for cryptocurrency networks. It seems like a closer analogy would be something like a contrived scenario with an airline that has routes which are absolutely static and predetermined (e.g. a contrived scenario where an airline decides it's going to fly a passenger plane a certain route once per day every day at the exact same time for a year no matter what, even if no one's aboard, and also the tickets are free if assuming no transaction fees). There are still the indirect issues with supporting the network, but it seems like there's less of a marginal emission concern if you're someone who's just making transactions, or arguably even no marginal emission concern.
In reality, you are adding some marginal emissions due to transaction fees (direct incentive to mine), and the indirect incentives could maybe be broken down into something marginal as well (no one using the network = no incentive to mine since the currency would probably have no value), but basically it kind of feels like there's less of a direct marginal emission concern as an end user of the network compared to something like getting on a plane, especially if you take transaction fees out of the equation. In that sense, it feels like abstaining is somewhat more of a moral protest rather than a direct economic "vote" or boycott.
Am I wrong about any of this? I probably am; this is just a random thought. Maybe the transaction fees are the crux of it (even if the block rewards are much more lucrative), so eliminating them from the equation for the sake of argument makes the whole point moot?