"Why are people in such denial over flying being so bad for the environment?"
I was wondering the same thing. (It is still more true of the climate impacts of having kids).
I'm pretty sure Mumsnet doesn't like seeing what it doesn't want to see. Posts that remain within a liberal capitalist paradigm are generally responded to - those that take a more critical stance to capitalist realism generally go whooshing over the collective head on here.
There are online tools you can use to calculate the impact of your flight. They will tell you how much Arctic ice you are melting. It will also tell you how what kinds of adjustments you'd have to make to offset it. See, for example:
shameplane.com
I don't know how many years of reusable toilet paper you'd have to have to undo the damage of a transatlantic flight, but I'm guessing it's more than a human lifetime's worth.
The idea that we can somehow buy our way out of climate change by making minor adjustments, and that doing very little is "enough" is laughable. No, it isn't OK to 'try your best' without making any actual, serious sacrifices. We need to decarbonise the economy, which is going to mean some kind of planned recession. It. Will. Hurt.