Whether Malthus himself was a right-winger or not isn't really important... it doesn't change how the trope of overpopulation has been used to protect power and privilege (ie, the whole point of right-wing ideology). For instance, there is a very good reason why white supremacists support the criminalization of women's health care in (supposedly) "white" countries while demonizing 3rd world countries for their (supposedly) "explosive population growth."

It's a very old trope that flattens human consumption and therefore camouflages the reality that certain classes of people consume resources at astronomical rates in comparison with the rest. It's utility in shielding class hierarchies from scrutiny should be perfectly obvious.