I suppose it never occured to these people that the Universe as a whole goes through changes.... many of which whose cycles are much, much, much longer than our lifespans and that our current perception of said cycle and the assumption that we are somehow responsible is just plain silly.
I suppose these people think the Ice Age was caused by man... even the "mini" ice age that resulted in the Dark Ages perhaps?
You can't stop cows from farting, it's part of the natural cycle of things. If you quit screaming "the sky is falling" you might have more time to enjoy your life little more.
It appears to be true (based on current theories) that some large species of animals were hunted to extinction by man (such as mastadons in North America), so we definitely have the ability to affect the planet in that sense. And while it is true that you can't stop cows from farting (a major cause of 'greenhouse gas' emission, LOL), there would not be so many cows if we humans didn't raise them as foodstock.
However, that does not mean that our activities changed the climate. I am perfectly willing to accept that it is possible, but I have doubts that it happened, or that it happened to the extent being claimed. I also have my doubts that anything can be done about it even if it was caused by us.
Everywhere are activists of one sort or another. Some want me to quit smoking (I did, but not because of them). Some want me to lose weight (ditto). Some want me to become a vegetarian (not on your life), some want me to recycle everything (I do what I can). Some want me to walk or bicycle to work (not possible for me). Some want...well, you get the idea. Some people complain about EVERYTHING. They don't like using fossil fuel for power, like coal and natural gas. But then they also hate atomic energy, and oh by the way hydroelectric power destroys natural habitats and keeps salmon from spawning and yikes, did you know that wind turbines kill bird of prey that fly into the blades? So in the end, they hate it ALL and apparently they want us to turn it all off and live in the freaking dark. And they don't get why others see them as feckin' lunatics.
All I want it to basically be left alone. I'm happy to do my bit for the planet, but I want to do it because I want to do it. I don't want it crammed down my throat by a bunch of do-gooders whose science is suspect anyway. I don't want to be told how to live by those who can't even agree on how it is I ought to be doing that. I don't want my current lifestyle seriously imfringed upon by those who think they have a better idea and that their better idea gives them the legal right to make me live the way they think I ought to.
I don't tell them to eat meat, smoke cigarettes, get fat, not exercise, or anything like that. I don't tell them what kind of car to drive or how to live. But they see nothing wrong with telling me these things. For them, I have a single-finger reply.