Milfurs are
furries who have served or are currently serving in
military.
This group of people may or may not influence to the army-themed furry art, or the infrequent discussion in furry newsgroups about "right to arm bears" (looks like the civilian furries, and much more likely the non-furries, are much more interested about such matters, though).
"The furries and the army have one thing in common... the muck..." - random comment heard in The Purple Nurple