I've observed that other groups are mainly selective with how/when they stand together. They have no problem separating themselves or uniting when it's to their benefit. Nationality, political affiliation, gender, religion, sexuality, financial status, race, ethnicity, and neighborhood are all categories those groups will flip flop with if/when it suits there needs.
If the conversation is about addressing the problems unique to a black American we should not be afraid to state so. Every group that has their own unique situation should be able to do that. If black immigrants want to support ADOS they are more than able and are welcomed as allies. If every thing was cool when African American merely implied that we were different, it should not matter when ADOS clearly defines it. I would consider it very unusual, even suspicious, if a person allowed something like this to turn their back on us to reduce whatever power we might have.
ADOS, as their website shows, is about fighting against the injustices and mistreatment of people, in this case black Americans. Why would that cause division from people that should already genuinely support us regardless of labels? It makes no sense as I think about it. If it does, I say they were probably not truly on the side of justice anyway.