Source for thinking the degrowth crowd thinks this: Introduction to “The Future is Degrowth”. Does the degrowth crowd really think they can get rid of capitalism without any violence? This seems to have the opposite of a historical precedent, and is a deviation in Marxism, which they seem to heavily draw from. Anytime revolutionaries took the peaceful road they got outcompeted at best and massacred at worst.
The irony about Malthusians is that their theories and worries would indeed come to pass if their ideas were to come into practice.