Today, many treat Malthus as a bad guy - morally and intellectually mistaken.
Malthus did advocate culling the poor by "facilitating" their mortality - for example by forcing them into overcrwoded conditions in order to encourage the plague. This doesn't make him a popular figure among modern thinkers.
Malthus was also concerned that resource limitation would lead to widespread human famines - unless something was done. In fact, since he wrote his An Essay on the Principle of Population - technological progress has outstripped human reproduction - resulting in a generally richer and less famished world population. This has led many to claim that "Malthus was wrong".
However, Malthus got a lot right. His big idea was that unchecked population growth would typically outstrip resource growth. This observation is both correct, and important. It is the basis of the basic biological idea of resource limitation.
People don't seem to want to hear that Malthus was right. The future availability of resources depends on technological issues that are not yet fully resolved - so it may legitimately be asked how the claim that Malthus was right can be justified. However, resources have a hard time increasing faster than time cubed - since that's how fast light cones expand. That's not fast enough to match the exponential growth of unchecked populations. Absent some pretty exotic physics, Malthus is right - by default.
Matt Ridley nominated "Malthusianism" as his scientific idea that is ready for retirement in the 2014 Edge annual question. By contrast, I consider Malthus to be a neglected and misunderstood scientific pioneer. He was ahead of his time. Following in the footsteps of Darwin and Wallace, we should pay attention to his views.
2016 Update: more Malthus denigration from Matt Ridley: The misapplication of Malthus.