There certainly are very good moral reasons not to pursue a certain sort of scientific research. For instance, it is not right to run certain kinds of psychological or medical experiments on people because of the risk to their mental and bodily health. Cases in which a subject has been scarred (mentally or otherwise) because of a certain experiment have been documented. A classic case is the famous Stanford Prison Experiment in 1971 which aimed to study the effect of captivity. A group of subjects assumed the role of guards and another group that of inmates. During the experiment, the inmates were subjected to abuse by the guards who grew increasingly sadistic. Some subjects were sexual humiliated and some of them were traumatized after the experiment was over. It is plain that this experiment should not have been conducted, even if the only way to test a certain psychological hypothesis depended on conducting it. Noone has the right to cause psychological trauma in others in the name of science. With sufficient ingenuity, one can find other less risky ways to test hypotheses, but especially in the field of social psychology this can be really tough.
And similar things also apply to experiments on animals. There are some very strict laws regulating what psychological and medical experiments one can run on human and animal subjects. Some of these are perhaps not completely reasonable and are due to being over-cautious in these matters, but there is certainly a need for such control over experiments.
Your posts seem not to be focused on ethical controls over experiments as much as controls over what theories can be made public (and research on them funded etc.). At least that's what the example of the different races/different species theory suggests. On that matter I completely agree. If we have on hand a theory that qualifies as genuinely scientific (eg. creation science may not count), then it can be made public and other researchers can work on it.
When I wrote "What we should be concerned with is the moral and political meaning and consequences of a certain classification", I certainly did not mean that there should be moral limits on what biological classifications we are allowed to make. This is a very unreasonable interpretation of my post. We are free to make any classification we like, as long as it has scientific credentials. There should indeed be no moral or political limits to scientific theorizing. But given a certain classification (eg. a classification of races into different species), we can ask the following question: if we accept this classification, are we or are we not entitled to take different moral stances towards other people on the basis of it? So in this particular case: if we accept that races are different species, are we or are we not entitled to take different moral stances towards other people on the basis of their race? This question is highly relevant to the discussion on this thread. My answer to it is: No.
It seems to me clear as anything that racial differences have no moral relevance. It is wrong, for instance, to allow different opportunities (education, jobs) to people on the basis of their race. And this is so even if it turned that races belong to different species. "It is not for you to say or anyone to dictate" could naturally be taken to mean that there is no right view on whether or not racial differences are morally relevant. If so, this would be inconsistent with thinking that racial differences do matter morally, which you seem to be holding. I am therefore unsure what it is you are trying to say here. Perhaps, making a moral judgment commonly carries a didactic tone, but I believe my claim above did not carry such a tone, as I have no didactic aspirations here.
It seems right to think that all moral agents have the same basic rights and responsibilities. Perhaps moral agents belong to different species - as would be the case if individuals from different races belong to different species. If an agent is threatening the well-being of any other agent, then it appears right for one to help put an end to this threat. (Whether this involves a license to take the life of the threatening agent is a vexed matter that I don't wish to get into now as it's irrelevant.) Yet, one cannot justly help put an end to the threat when the threatened party is of one's own race and not help eliminate the threat when the threatened party belongs to another race. If a white threatens a black, I am obliged to help remove the threat just as I am obliged to help when a black threatens a white. It is unjust to put members of your race first, even if all and only members of your race were to belong to the same species as you.