You shouldn't oppose reviewers unless you have reasonable belief that they'll be biased against your paper. That might be because they're biased against you, your particular sub-field or the techniques you've used; or, in cases such as this one, if they're very sensitive to any kind of criticism. In this case, we can be pretty sure that they're not biased against your sub-field (they wrote papers in it themselves!) or really against your techniques (that doesn't seem to be a thing in mathematics, but more likely in experimental sciences).
Simply being proven objectively wrong shouldn't cause significant bias for most mathematicians. Of course, it's embarrassing to have published something wrong. However, it seems that the error wasn't central to the original paper, or they'd have tried to write an actual proof without the supposedly redundant assumption. It seems to have been more of an aside, so the level of embarrassment we're talking about is "Oops, I made a boo-boo" and nowhere near "Noooooo! My career is destroyed! I must bury this!"
The authors of the claim you showed to be wrong are likely to be particularly good reviewers, since they understand the topic very well. I'd expect the natural choice of reviewers would include one of those people and one outsider.