Because global warming means not just a slightly less comfortable summer season, but also rising ocean levels that displace low-lying coastal communities (to include not just island nations like Micronesia and The Maldives, but also large sections of major harbor cities like New York City, Los Angeles, Mumbai, and Sydney); more violent and more frequent tropical storms and monsoons; drastic changes to crop viability in semi-arid agricultural regions such as those in California, North Africa, Yemen, and Afghanistan; increased wildfires in California and Australia; worsened air quality in and around major cities (especially megacities); acidification of our oceans; and heightened turmoil in and around arid regions with existing water and refugee crises.

I think there's a latent suggestion in your language that reducing consumption discards all of the technological social progress of the past three centuries, while climate change presents a negotiable inconvenience. The balance is quite the opposite. You can keep cellphones, the internet, food security, modern medicine, and clean, running water. If anything, many of these advances are secured, rather than threatened, by curbing human-driven climate change.

>If you want to go back to stone age, please feel free to go: I'm not retaining you.

Beyond misjudging the gravity of the problem at hand, I think this comment is also a little short-sighted in appreciating the nature of the problem and our collective responsibility for it. The choices we make as consumers, designers, and voters have impacts that affect the whole world, including populations with clear stake but no voice in those decisions. It's particularly callous to tell someone whose island will be washed away by rising sea levels that they're free to eschew any technology they want to curb ecological impact while our own emissions (by absolute value or per capita) far exceed their own contribution to atmospheric CO2 levels.