People (=male doctors) postulated that when women are emotional or horny, that's a sickness called "Female Hysteria".
It was caused by the womb wondering around inside the body.
The cure was to trigger "Hysterical Paroxysm" by a doctor stimulating her genitals with a vibrator.

Not exactly a scientific debate, but among the general public there was strong opposition to the idea that rocket engines would work in space, where there’s “nothing to push against.” Famously, the New York Times editorial board mocked Robert Goddard (the rocket scientist that now has a NASA space flight center named after him) in a 1920 article:

“That Professor Goddard, with his ‘chair’ in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react — to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high schools.”

Image of the editorial

The New York Times eventually formally retracted that op ed, on July 17th, 1969 - while the Apollo 11 crew was already en route to the moon. The retraction is pretty funny:

Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error.

Retraction source

The funny thing about heliocentrism is, that isn't really the modern view either. The modern view is that there are no privileged reference frames, and heliocentrism and geocentrisms are just questions of reference frame. You can construct consistent physical models from either, and for example, you'll probably use a geocentric model if you're gonna launch a satellite.

But another fun one is the so-called discovery of oxygen, which is really about what's going on with fire. Before Lavoisier, the dominant belief was that fire is the release of phlogiston. What discredited this was the discovery of materials that get heavier when burned.

Ignaz Semmelweis tried to convince the medical establishment that washing hand stop'the spread of disease in hospitals. His colleagues responded that doctors are gentlemen and gentlempdo not have dirty hands. Semmelweis was committed to a mental institution soon after and died from an infection as a result of a beoti'he received from institution workers. A few decades later the four humors school of medicine was replaced with diseases caused by microorganisms.