What you see here is a common argumentative tactic by climate change deniers: "Scientists have been hysterical about global cooling in the past and that has not happened. Therefore claims about climate change in general are not to be believed."
I refer you to the wikipedia article on global cooling for reference. Especially take into consideration the line chart at the very top.
https://en.wikipedia.org/wiki/Global_cooling
With regards to the Paul Ehrlich quote I would add that he is not actually talking about climate change at all but overpopulation.