please explain how I'm wrong.

I think the misunderstanding at play is that this isn't a question of foreign relations, but rather about the factual conditions of the conflict and whether they justify the legal and/or moral label of genocide.

Such factual conditions can be investigated through sound, empirical gathering of evidence, and any well defined concept of genocide can then be evaluated in that context.

This evidence gathering and following genocide evaluation can be much better performed by organizations with expertise and authority on such matters. Most of the listed organizations are considering expert evidence gatherers and experienced, empowered authorities of genocide evaluation.

Therefore, the fact that such a list of organizations agree on the evidence supporting the label, must weigh as evidence to those of us who do not have this expertise ourselves. It proves nothing outright, but should weigh heavily in the private opinion-forming of laymen.