Seems like the concept of collective guilt is creeping in here.
While I don't dispute that the Wehrmacht as an organisation was complicit with/responsible for various war crimes, that doesn't mean that all individual members were complicit and therefore effective summary execution is itself a war crime.
I agree with you on this point of collective punishment btw, not all individual soldiers in the wehrmacht were war criminals deserving immediate execution, but it's worth mentioning something here which is often overlooked:
After the war this myth was allowed to develop that it was Hitler and the Nazi party alone responsible for both the holocaust and losing the war, and that the German generals in the Wehrmacht were merely good patriotic German soldiers loyally following the orders of the Nazi party, and that actually if only Hitler had listened to his generals they'd have not only won the war by 1942 but could done so without any kind of holocaust (which of course the generals were totally unaware of and were horrified by). This is bullshit of the highest order, and has become one of the biggest sustained myths of world war 2. You can trace it back to the self-serving lies and bullshit that the German generals produced for the Americans post-1945 when they were interrogated and debriefed, and sadly from this point it seems to have stuck.
But in actuality the wehrmacht was complicit in all the crimes of Nazism. Hitler's policy of war wasn't devoid of meaning, from the very beginning Hitler's war had purpose - to destroy bolshevism, to found a Germanic "1000 year reich" that would politically unify and dominate Europe as the master culture, and to bring about a worldwide demographic revolution which necessarily involved the massacre of the Jews, and other "untermensch" along with them. Those generals were well aware of this purpose, they knew why they were fighting and as far as anyone can tell from looking at the actual historical record (as opposed to the post-war shite they later came out with) the generals in the German army were enthusiastic supporters of these aims, made no attempt to circumvent them, and whilst the war was going in their favour actually enthusiastically supported them.
This is perhaps my biggest criticism of the film Downfall, that it panders to these myths a little bit. Whilst some criticised this film for humanising Hitler actually the part of the film I disliked the most is the way in which they humanised the generals, both SS and wehrmacht, again clinging onto this type of ahistorical nonsense that Hitler was solely to blame and that the generals were all decent men being forced to carry out his crazy orders. This is not the case - and infact it has some parallels with the "stab in the back" stuff that followed the first world war, that it wasn't the utter incompetence and stupidity of Hindenberg and Ludendorf that lost the war it was some other external group that betrayed these fine generals from the victory they so clearly deserved, in that case it was Jews who were scapegoated by after the war, in this case Hitler shoulders all the blame for these gross tactical errors not the Generals.
And just like world war 1 the competence and conduct of the Wehrmacht was never called into question, it was always this idea that Hitler was some imbecile who wouldn't listen to the sound and pragmatic advice of his generals rather than their fault that seemed to stick. At the end of the first world war the conduct of Hindenberg and Ludendorf was self-serving and disgusting, but they ended up coming home as war heroes because they successfully found a scapegoat, and after the second world war something similar happened except that it was Hitler personally. Another myth that comes up as a result of this is that Hitler was some tactically inept fool who ignored or bullied his generals sound advice, actually this isn't true. For starters the single most impressive tactical decision made during the war, the decision to attack France using a small number of fast and mobile mechanised divisions to go straight through the maginot line rather than through Belgium, where the French army was amassing, thus cutting off the bulk of the French army from Paris and causing total disarray, was Hitler's idea not his generals. Likewise the idea that Hitler refused to allow German soldiers to retreat is also a myth, from time to time he certainly did allow them to retreat, and this notion of his furiously refusing to allow these tactics was only really true by the beginning of 1945, by which time he had started to lose his grip on reality and of course by this point the war was lost. Some of the worst tactical decisions of the war were as a result of Wehrmacht generals giving incredibly bad advice, all of which gets badly overlooked.
Anyway sorry for the digression it's not really the thread for it I know.