Actually, it is true. According to the Antarctic ice core data CO2 levels spiked just short of 300 ppm the last three inter-glacial maxes. We are above 400 ppm now. The point is, that is not causing temps to increase accordingly. As the ice core data also shows, CO2 levels are a lagging indicator, not a leading indicator.
Yup, CO2 levels rise after warming, and are not the cause of warming. Additionally, think what 400 ppm means. That's a few parts per 10,000 parts. Essentially nothing, miniscule, far below tiny. 1/25th of one-percent. As if that would cause the world to die. CO2 ebbs with rises and declines, affected by animal and plant life. The Earth knows how to deal with it. If mankind attempts to reduce it, then plants die and you have a bigger problem than perceived problems that just aren't so.