Not too bizarre, both groups were Nationalists, so I presume that they saw that cooperating on their common objective (total racial segregation) was more useful

Not too bizarre, both groups were Nationalists, so I presume that they saw that cooperating on their common objective (total racial segregation) was more useful in the long term. Interestingly, both George Lincoln Rockwell and Malcolm X were assassinated by members of their own parties (a former one in Rockwell's case, though). Sadly, I don't know much else about them.