Belgium controlled the Congo in the early 1900s and used slave-labor to extract rubber. There's a ton of documentation on the atrocities committed. Things like stealing all the children, then sending their parents the severed hands of their kids and telling them if they didn't meet quota they'd get feet next.

It's not like other colonial powers weren't also incredibly evil, but Belgium's crimes were quite recent and well-known (both now and at the time). Very much like Israel!