You are right about one thing. Humans are ill equipped to care about the welfare of those beyond their small tribe. But that's why we form governments and appoint leaders. They are supposed to look out for the greater whole.
As for your Climate Change alarmists, I take great exception to that and consider it a great fallacy. It is easier to sow doubt than to convince someone of a fact and that is what deniers have preyed upon. If you don't think we are all going to be fucked as a species in the next 100 years then you sir or madam are part of the problem.
And there is no overstating. The facts are the facts regardless if those facts take 25 years, 100 years, or 200 years to catch up to us. It's going to happen. We are putting BILLIONS of metric tons of a greenhouse gas into the atmosphere every year for damn near a century now. The ONLY way you don't draw the same conclusions that 99% of scientists do is because a) Your basic knowledge of how greenhouse gases work is deficient or b) you clearly have an agenda and purposely adopt an ignorant position.
The reason alarms are raised is because there is a huge lag when it comes to the effects on the atmosphere and the climate. So if we wait until shit is so obviously wrong that even the Koch's admit it then nothing we do will ever reverse the damage.