NFTs do not cause carbon emissions themselves, just like you don't add carbon emissions by occupying a seat on a public transportation bus. The bus is doing its daily route and has a fixed amount of emissions per day whether it has any occupants or not. This analogy breaks quickly, so I wouldn't look too much into it.
Maybe a better analogy is to think of your WiFi router. Its energy use is (predominantly) static regardless of how many packets you route through it. So by browsing, you are not causing additional carbon emissions.
In more technical terms: more transactions do not cause more hashrate. Ethereum's CO2 footprint does not scale with transactional count. So asking people to use the network less will not cause the hashrate to go down. The only way you reduce energy consumption is by getting miners to mine less, which triggers the protocol to adjust the mining difficulty accordingly. As laid out above, this has nothing to do with how many transactions are happening on ETH, or whether NFTs are being minted on it.