I'm actually quite proud of being a very long time cuckold, for 47 years now, and I married my wife 37 years ago knowing she was seeing other men since our first date. Not everybody has a wife who has slept with well over a thousand men, and out of all those cocks, she chose mine to be married to.
I do agree that it would usually be an insult to call someone a cuck if they aren't one, but in my case I am one. Most men aren't very happy if their wife fucks around. For me, I don't know anything about the "Alt-Right," and first heard of it a few weeks before the election. I haven't ever heard anybody actually use the word cuck as an insult.