Hey, with these steps you can play the campaign as germans, including the skirmishes:
1: launch the game with "-entry_race germans_campaign"
2: start new campaign (disable tutorial! important!)
3: save
4: exit game
5: start game without arguments
6: start new campaign
7: load previous saved campaign
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Now you can start skirmishes / missions without the scar error.
I was not able to start the Pomigliano Airfield mission, regardless of US, british or german company attacking, so you have to naval or artillery bombard it until you can take it over with an infantry unit without a skirmish. (the "play" button stayed disabled on that mission for me) - counter repair Naples with an engineer / pioneer unit if u need more time. All following mission worked fine for me.
I followed your instructions and played around 2 hours of the campaign with crashes only occurring during matches and so forth now as you can see here:
The only difference is that I had to use an engineer unit to capture the airfield because a normal Grenadier section didn't want to for some reason.
Can't say any time I ever chose Ostheer in my 600+ games of them in CoH2 that I was ever on a power fantasy about the Nazis ruling the world. Instead, I simply enjoy the design of the faction the most (the need for combined arms to win, the feeling when you bring a fresh tiger tank on the field, et al.) Similarly, when I play Germany in games like Hearts of Iron, it is because it is funner to be the aggressor than it is to sit around and wait for things to happen.
You could argue that this is just me, but somehow I find it doubtful that every Ostheer player other than me is some kind of undercover racist. No idea why your inclination is to simply say people who enjoy playing Germany must be as you stated, it is odd to immediately try and paint a collection of people in such a light.
Honestly people called me a Nazi when I had an American flag in the background of my avatar so it doesn't really matter who you are or what you do or what you say, hell I've even seen jewish people be called Nazis lol.
So the best thing that you can probably do is just ignore these type of people because they truly believe that whoever doesn't agree with them is a Nazi, fascist or a racist or whatever.