This is not a convincing argument, but even if it were, carbon recapture is currently even more of a "rounding error" in the grand scheme of carbon emissions. Current carbon emissions are somewhere around 50 billion metric tons a year. I've seen varying estimates of crypto emissions, so I'm going to cite one [1] on the low end here, since it's more favorable to your argument, but the highest I've seen is less than double this number, so they're all in the same ballpark.
ETH currently emits 7.4 million metric tons of CO2 a year. Bitcoin is much higher. I've seen estimates as low as 16 million and as high as 55. There are other chains as well. To keep the math simple, let's round it to 50 million, so crypto is contributing 0.1% of total carbon emissions. Like you said, a rounding error.
I think we're just going to have to disagree on mitigations. I don't think they're working very well.
Crucially, at the beginning of 2019, according to the source I linked, ETH was only at 2 million tons a year. It's more than tripled since then. In 2021, Carbon recapture removed an estimated 9 thousand tons of CO2. [2] The CO2 from the growth of ETH eclipses anything that carbon recapture is currently capable of. The technology will get better. The most optimistic estimate I've seen is that carbon recapture will hit 30 million tons a year in 2070. But this year, Stripe Crypto only has to increase crypto transactions, across all blockchains it supports, by 9,000 tons to completely offset all of the money it's putting into recapture efforts. Even if you remove all the other chains, Stripe only has to increase ETH transactions by 1.3% to achieve this own-goal.
Long term, Stripe alone could end up causing more CO2 emissions on the blockchains to grow faster than all of carbon recapture.
1: https://kylemcdonald.github.io/ethereum-emissions/
2: https://www.reuters.com/business/environment/worlds-largest-...