In any case, since this is a counter-argument that may eventually get raised

Rather than a counterargument, it just seems like confirmation of Eliezer's argument to me. Nature imposes regular pain on humans, humans invent reasons why it shouldn't be otherwise. Yes, not everyone spends a lot of time justifying it, but how many people spend a lot of time justifying death?

Yes, people may try to alleviate the suffering somewhat, and even have some success, but they also tried to treat diseases (with even some occasional success) back in the day when they thought those were a good thing, too.