Tl;Dr c is closest to what you're asking but it's more like.

(D) Kroupka is making bold claims that have to be verified first in the scientific arena very loudly and publically. That is odd.
He is claiming that DM doesn't exist which is effectively saying the particle solution to the problem can't exist. This breaks the big bang model as we understand it as I've stated. And is offering a gravity based solution which explains some small phenomena which he claims that not only that this isn't modelled accurately currently but that it can't be using the DM models. That claim requires huge effort to correctly simulate the matter field as it _might_ exist and that requires more assumptions. This could mean certain particle solutions are ruled out or that we need to revise the particle model (fantastic we learned something), but it's much less likely that it's completely dead just because one test says so.

His model may be valid. His data might be good. His conclusion has little to do with either.

Just because a theory doesn't match all observations doesn't mean people stop working on it. If that happened the foundations leading to the Higgs scalar boson wouldn't have been researched as at the time everyone was interested in understanding other field theories.

Ok some background.

DM research was introduced as a solution to the problem of the distribution of mass within galaxies. I.e. orbital velocities of stars within a single galaxy.

In order to try and understand this phenomena models were used to simulate the distribution of "matter fields" within galaxies.
Now modern modelling has evolved to simulate complex systems of multiple galaxies or even larger.
We now suspect and have strong evidence for huge mega structures (MPa mega parsecs in size) made of some "DM goop" in the universe.

Modeling of this is notoriously difficult and relies on numerous assumptions because we can't model everything exactly so we take sensible shortcuts which shouldn't impact the physics of interest for the simulation.

Large simulations have problems the further they evolve. This is a stochastic not model dependent statement. Modelling a thing we're yet to observe is even more difficult.

Most claims that DM can't exist are people modifying gravity in some way to remove DM as a physical particle that you can build a DM hammer out of in principle. These claims are not entirely baseless but really struggle when you try to match large gravitational structures we have seen so far in the universe (cosmic filaments).

Kroupa claiming his simulation has to be the only simulation to explain a problem (if he makes or infers this) would be false. Everything in science has requirement of reproducibility which goes beyond share the source and run the tool.

Kroupa claiming that his model perfectly describes this set of observations might be interesting, but is yet to be demonstrated at different scales. Again this has to satisfy orbital momenta of stars within a galaxy as well as demonstrating larger scale effects such as gravitational lensing.

Dark matter simulations _all of them_ will have some amount of disagreement or uncertainty. That is the nature of scientific computer modelling and comparison to scientificly collected data. Uncertainty and error estimation/understanding is a huge part of this field. Anyone claiming exact results better have a huge amount of data to back it up.

This is either a conversation that would have been easier by Skype. I'm guessing you don't have a strong background in a formal science. I'm not saying this from some pedastle, it's a joint question/observation of you focusing on the socialogical implications and exactness of a thing.

There is no lack of interest from experts to talk about their field. There is almost never a lack of wanting to move away from the "status quo" in the scientific community. Especially in blue sky particle and astro research at a professional level. The public perception of this existing comes from 2 issues. 1) "loud" individuals who shout loudly that they're not being heard will be ignored. That isn't discourse, that is someone acting like a small child within this area. Unfortunately they often get awarded by funding and we're stuck with them. As they get pushed aside for shouting rather than discussing they tend to get louder. 2) the media loves to paint the image of scientists sitting there as gatekeepers to some theoretical framework. This is fun in movies etc but mostly we talk about this in science education as a case of remember the mistakes from the last 100 years. As a result you will be looked at strangely for dismissing an idea out of hand without proof or testability.