As the government becomes a shareholder, it can do as any shareholder desires and formulate demands for the management.
You are both right and wrong at the same time. It isn't a shareholder making a demand of management, but a future investor conditioning its investment to a management promise to take (or not take) a certain future action to the benefit of another company in which it has a stake. That is business as usual... Many investors want the companies they invest in to buy from one another (exclusively) to the extent possible.
The major difference is in the enforcement mechanism. Whereas a private investor would have to balance the cost and judgment risk against the potential benefits of seeking relief from civil courts, governments have far more options to deal with perceived or real transgressions from their decrees, starting with nearly unlimited funds for legal action without significant concern over the outcome, all the way to, in some instances, relying on the criminal justice system to punish individuals. With a private investor, Lufthansa could potentially get away with vague promises or even a contract and take a chance and do the opposite a year or two later… but with the government as shareholder, the degree will be followed to the letter until it expires (if an expiration date is set) or until the government issues another decree to nullify the first.
I hope Trump retaliates: Boeing orders only as a condition of future bailout funds.
Wouldn't be so much a retaliation as an escalation since the German government did not explicitly state that Boeing orders should be canceled (though the net effect is probably the same). That said, Trump isn't known for its measured approach and I do think that if he were to intervene, escalation would be his approach. The thing is, I think the pandemic and Trump's total unpredictability (going from all bite no bark to totally reversing the world order and back on a whim) have changed European governments' attitude, especially Germany. If Trump escalates, the best outcome would be for the EU to sit and wait out the results of the election in November. I wouldn't be surprised if EU governments choose not to and slap their own ban on Boeing aircraft sales in the EU. Add to it that China has been threatening to cancel all Boeing orders (and for once, thanks to the pandemic it is a threat they can afford to act upon), and Boeing will need a massive bailout from the US government to survive.