Denail of Germ theory was slothful induction?

We need to "unlearn" the fact that John Snow is revered for his discovery and treat him just like another scientist, because, in this hypothetical, germ theory was not yet established. This is just an attempt to remove the bias of hindsight (of course, it would be foolish given what we now know).

Now we need a quick primer on some concepts in scientific methodology. The idea of "accepting" a theory is always done provisionally . In other words, we can say, "Yeah, this makes sense to me, more so than the null hypothesis, so I will view it as the best explanation given the current evidence."

Another important factor is how much of the scientific community had an opportunity to review the theory. If the reason for the lack of consensus was that Snow just came up with the theory, then the biologist friend should rely on his own professional opinion. However, if a good portion of the scientific community reviewed the data and rejected the claim that this was a "very strong case," then the biologist friend should seriously consider that he might be misinterpreting the data and coming to a wrong conclusion.

So back to your question. I would say "it depends," and request more information. If the biologist friend refused to accept the data provisionally, AND the reason for the lack of consensus was novelty (very few scientists reviewed it), then a strong argument can be made for slothful induction. If, on the other hand, the biologist friend refused to accept the theory because a significant majority of his peers (perhaps 80+%) reviewed the data and provided reasonable critiques that need to be investigated, then the biologist friend should consider that they are missing something that others are seeing, and not accepting the theory would be reasonable and not slothful induction.