Yeah but it being dumped, in the abstract, doesn't matter. It is like complaining that there is a desert or an ocean - there are places on the earth that aren't good to live in. An electronics dump somewhere doesn't rate compared to something like the Pacific Ocean in terms of how much landmass gets sterilised.
This waste was dumped. The fact that poor people moved to the dump to make a living scavenging is a secondary phenomenon. Without them it still would have been dumped.