

As someone else said, they pay royalties. Secondly, because they are not costing musicians their jobs. DJs aren’t stealing artists jobs, music labels aren’t dropping musicians for DJs, and DJs are at least putting some level of effort to create something (which I will admit is debatable and the weakest argument).
I don’t necessarily see the issue with codemning behavior based on modern standards. There were people at the time who (while yes were ahead of the majority of people (in the US at least)) opposed slavery. I feel it is entirely fair to extend the belief that those that believed in slavery were morally wrong even for the time.
I feel a modern parallel (not perfect but I mean what is for American slavery, it was that fucked up) is trans rights. Trans rights is a hot button topic that is highly debated, similar to slavery or any other hot button topic through history (civil rights, women’s right to vote, etc). Those that oppose trans rights are yes a product of their time, but that doesn’t mean they aren’t morally wrong and shouldn’t be held accountable for those beliefs.