In Stalag 17 Billy Wilder takes a stand to speak out against the abuses he saw, relate this to America's Cold War policies and social environment and address how this type of critique may or may not be applicable to today's political climate.
I think that you could see the movie as a criticism of the way that people in the US were quick to suspect others of being communists in the McCarthy Era. The William Holden character is condemned by all the others on circumstantial evidence and because he is different than all the other prisoners. I think you can argue that he's supposed to represent people suspected of being red simply because they're different.
I don't think that today's political climate is like that. We don't have any one thing that you can accuse someone of to stigmatize them the way you could in the '50s. You can say Obama's socialist, but most people know that that's just partisanship just as most people realized that the Democrats' more strident criticisms of Bush were partisan.
I do realize that we have a pretty toxic political environment right now, but it's not at the point where you can ruin someone simply by alleging that they are a communist or a Muslim or whatever.