For example, if the world was ending next year it might make sense to turn off all fossil fuels and eradicate most of the human population. But if it is only a few degrees per century we can consider… better options.
Let me rephrase: realistically speaking, the things humanity will manage to do in the next 10 years will be such a lukewarm attempt that the chance we will "accidentally" overshoot and create more misery is close to zero.
We already created misery via starvation due to biomass subsidies, what makes you think our future policies will be harmless?
Of course my example was absurd, but it illustrates the trade offs involved.