That’s actually a myth. Global cooling was a small minority of published papers in climatology at the time. They were many more papers discussing warming.
Source: https://ams.confex.com/ams/pdfpapers/131047.pdf
P.S. I learned this watching the excellent video by Veritasium on climate change misconceptions:
http://www.populartechnology.net/2013/02/the-1970s-global-co...