Not saying I agree with the person you’re responding to, but I think you’re misinterpreting their point. They’re not trying to do a comparison between yearly emissions of T Swift and the average American, but attempting to demonstrate that there may be justifications for the amount of emissions.

Their comment seems to be suggesting that with the extreme demand to see this artist, her job requires she travel much farther than the average American. You could put some of the blame on her directly, but equally, we can factor in how many people are contributing to the extreme demand to see her. If you were in her shoes, could you resist the desire to perform and please your fans (and get paid for doing so).

Again, not trying to support a horse in this race, just to explain the point in more equitable terms.