Plants and humans both love water, but you can still drown.

Good news, everyone! ~450 ppm is far from the 10,000+ PPM that is toxic to humans or animals. (That's 4.5%, for the math challenged.) At this rate of increase you'll be "drowning" in a thousand or more years, I guess.

It's also 1/4 of the approximate 1,600 PPM that is optimal for a large number of plants to grow. In other words, the current levels are actually very low, compared to what the plants evolved to use.

Increased plant growth from more CO2 results in more biomass, thus more CO2 uptake, so it's a virtuous cycle and you'll be OK after all.

Please attempt steelmanning the global warming greenhouse effect and its consequences as an intellectual exercise.

No clue what sort of argument you're attempting to make here.

My post as entered is correct.

He was asking you to try to 'steelman', or take seriously the strongest version of, the arguments of your counterparts, rather than being dismissive.

"Plants like CO2" is not a counterargument to "Increased atmoospheric CO2 will have a number of outcomes that are net negative for humanity", so I presume they're asking you to actually think about the argument being made and respond to it, not some other, made up one.

Where do i even begin to respond to this?

Plants growing slightly faster does not mitigate the many consequences of increased CO2.

Nitrate is a plant food too, doesn't mean it's not killing large parts of the ocean.

I didn't call you anything, I wasn't even talking to you.