Race is as discursive a phenomenon as national identity. Its basis doesn't make it any more "real"; they're both wrapped in impenetrable layers of arbitrary meaning.
Racisim is based, obviously, off of different regional ethnicities. You look at Africans, they have dark skin. Europeans have light skin, etc. This
is a tangible difference. While beyond statistics, it doesn't mean anything, you can tell to within the continent (usually) what ethnicity people are by looking at them. Simply put: no; race isn't arbitrary.
Nationality, however, is almost always completely independent of race. You are the same person, whether you are born in Austria or Germany, or Belgium or The Netherlands. Nationality is based off of what nation you are from, and nations are usually not restricted to specific regions or types of regions. They are arbitrary. Look in the Middle East, for example. Great Britain pretty much blindfolded themselves and drew random lines on a map and those were the borders of the countries.
I certainly hope you get what I'm saying.
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And about the m16 vs AK-47 debates, AFAIK, most of the M-16s are crap because they're unreliable arguments were made based on some of the first models of the rifle, which has come
a long way since then.