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The replies to the arguments opposing chimp testing haven’t tried to show why the defense of such testing is right from a nonspeciesist viewpoint. Rather, they’ve assumed that viewpoint.

Explaining all the arguments against the idea that speciesism is wrong would require lots of space. So I’ll just say here that if we are concerned with wellbeing it is arbitrary to take into account only some of them simply because they are possessed by certain individuals, rather than other ones.

I do indeed hold what you call a "speciest" viewpoint. Chimpanzees are worthy of moral consideration, but a human does have moral worth than a chimpanzee. Chimpanzees, likewise, have a greater moral worth than a lizard, and I would willingly experiment on lizards in order to improve the lives of Chimpanzees.

Additionally, Humans aren't treated as more special because of a completely arbitrary reason: they have more moral weight because a human, because of its intelligence, is more capable of making the universe a better place than a Chimpanzee is. Sacrificing a Chimpanzee to save a human is a similar ethical question to the trolley problem.