While these countries may legitimately harbor racial biases when it comes to immigration, you also have to consider the impact that illegal immigration from Africa has had on these countries and the EU as a whole. This might also play a big part in their actions. It's similar to illegal immigration through our southern border. In a nutshell it's economically draining (especially when you consider some of the countries failing right now) It just so happens that their illegal immigrants are predominately black, while ours are predominately brown. Now, whether or not this is their prime reasons for backing the rebels, I think that, while it may play a part in these European countries' motivation, I think that there are several other factors playing a larger part (mostly political and related to oil). Still, I haven't seen any evidence either way, and it's not like a country is going to openly state their motivations, so you might be right here.