I come from a huge military family, and I get what you're saying 100%. Fighting a war as brutal as vietnam, when it was basically kill every military aged male that you see before they kill you, you're obviously going to resent that nationality after watching them kill your best friends, and being put through the s**t you were put through. It's not the "right" way to think, but unfortunately it comes with the territory. I know quite a few infantrymen that have fought in iraq/Afghanistan and they all can't stand muslims. They understand that it's biased and racist but they just don't care after what they've seen. Imagine spending years with one specific nationality trying to kill you and your friends, the post traumatic stress alone would make everything from hearing their voices to seeing the way they dress, harder than you'd think.
I hate that it is that way, because I don't resent those people as a whole because I didn't fight them in a war.
Prime example, my friend was a sergeant in the marine corps. He was a grunt through and through. His profile picture is a picture of a dead pig with a copy of the quran in its mouth.
For his birthday party last year he held a barbecue and smoked an entire pig, calling it a "f**k muslims" party, and a s**t ton of vets came. It's crazy to see.