Sure, there are probably some doom-mongerers that spread horror stories about how we'll turn to Venus if we don't stop (we won't in the next several dozens of millions of years), but that has never been the threat from climate change. Besides, ideal for plant life doesn't mean ideal for human life, or life overall.
Think about the 9 billion mouths to feed man and the increase in arable lands too!
But won't too much CO2 make air quality too poor for humans and animals? And what about rising sea levels?
There's no delirious effects for human respiration shown at CO2 concentration levels below concentrations of 5000 ppm ...