Then they believe that war and poverty are good.
Mathias had them as positive checks against overpopulation.
To them medical breakthroughs are bad as they lead to over population.
Malthus didn't apply any moral judgements, he merely observed that when populations get too large, some factor will come along to reduce it, be it starvation, disease, war or whatever.
Malthus was actually an Anglican clergyman as well as an economist, and his theories were heavily criticized by Marx and Engels, among others.