Ep. 031 - Destiny Calls

[Areku]

I also was surprised Austin didn't get why Shinn joined the military it makes perfect sense to me and it seems silly of him to go and say Shinn should have joinned Orb's millitary.
When Orb were the ones who acted defiantly to the Alliance and got invaded by the Alliance which resulted in events leading up to Shinn's family being killed in cross fire.

Actually, I don't see how you could come to that conclusion. By the same reasoning that the confrontation that got his parents killed was the result of Orb's insistence on neutrality (and ultimately independence), so too was the whole war caused by the Plants' insistence on autonomy throughout the preceeding decade. Honestly, the only thing that makes any sense is that Shinn simply got caught up in anger and hastily decided to join the only major military that didn't directly participate in the battle that ruined his life.

[Mu La Flaga]

That is a true point since it's not like he would join the Earth Alliance or Orb's millitary and that just leaves ZAFT really.