i agree.  i think the difference is that 難民 refers to groups of people (e.g. in a camp), whereas 亡命者 might refer to Ayaan Hirsi Ali, say.

What other sorts of refugees are there? I think this amplification is not needed.

GG5, 大辞林、広辞苑「亡命」

Add political connotations (egs and gloss).
(Contrast with 難民, say.)

@@ -12,1 +12,1 @@
-<gloss>refugee</gloss>
+<gloss>refugee (e.g. political, ethnic, religious, ideological)</gloss>
@@ -14,0 +14,1 @@
+<gloss>émigré</gloss>