Even if we humans ill-advisedly bugger around with geo-engineering things we don't understand, there will still be change. So why the drive to resist the change?
The only logical answer is: for money. The people who are profiting from the status quo, want to continue to do so. Another group of people are seeking to profit from the fear mongering.
We should be wondering why there isn't a push to come up with means of adaptation. If sea levels rise, how can we reasonably evacuate lowlands? What is the impact on power generation and how do we manage that? Will there be an impact on food production and if so, what can we do about that?
Think about that last one: which is seems more reasonable, stopping the (poorly understood) climate from changing, or the (well understood) adaptation of crops to a new climate?
Fact: whether we geo-engineer or not, the climate will change, as it has always changed. So, do you want to spend your money on trying to prevent the inevitable, or do you want to spend it on something achievable?