A friend refers to another scientist as his best enemy. The important thing about this is, he is not angry or upset about the other scientist. I'll call them John and Jane, John being the one I know. John and Jane are both outspoken people. Consequently, at meetings the two of them spend a fair amount of time disagreeing with each other. And they disagree vigorously.
That vigor is part of what makes Jane a best enemy for John. John's not a quiet person himself. So it would be easy for him to vigorously say what he thinks is true and other people to quietly agree, because no other ideas were presented, or to quietly disagree. Quiet disagreement would be worse. It would mean that John would not have a chance to explain the parts of his thinking that would persuade those people that he was right after all. With a vigorous enemy, however, John can be confident that Jane will bring up those points that aren't clear to other people. And then John can explain them. After this, if anyone disagrees with him, there's a fair chance that it's because he doesn't really have things right himself. And he also has a chance to change his thinking, to arrive at something even better than what either he or Jane thought were the case when the two started their discussion.
The even larger bonus is that whatever conclusion John and Jane reach personally, they're confident that the entire audience knows what is the real topic of discussion, and why they each think as they do. This puts enough substance on the table for the audience to be making good decisions. If John's position isn't the one that some in the audience walk away with, that's fine. He's going to keep thinking about the topic himself and maybe decide that something closer to Jane's original position is more correct. Or maybe he realizes that there's a better way of describing why he thinks as he does. Either way, some scientific progress is made.
Another part of what makes it work is that their discussions, regardless of how vigorous (an uninformed observer might say 'violent'), are technical. Both of them have serious professional reasons for their conclusions. And it is those professional reasons they turn to, not cherry picking starting points for time series trend analysis and other dishonest or ignorant methods.
A final matter that makes it work is that neither of them is personally upset by the fact that they have professional disagreement. Both apparently rather relish it. After spending 8 hours at the meeting disagreeing with each other about almost everything under the sun, they go out to dinner together and chat pleasantly about other topics.
Strictly speaking, I only have 'John's view of matters. I don't know 'Jane'. Still, they've been doing it for decades now, and I think even of 'John' were extremely clueless about other people (and my observation is that he is fairly clueful), he'd have picked up on 'Jane's differing viewpoint.
Names and genders may well have been changed for the purpose of the story telling. The people and descriptions are otherwise accurate.