I always found German unions pretty good.
I mean the union is correct in this case. Robots will replace jobs. A union’s job is to make sure there are jobs for people in the company they are already in.
Usually unions would speak the truth (“robots = jobs go away”) but pair this with some suggestions: eg trying to upskill the affected worker so that they can be moved to a different department).
While I was working in Germany I always felt better at a company with a strong union.
The main problem with unions in Germany is that they block companies from adapting to changes in the environment quickly. Companies become heavy behemoths and end up suffering from it, which ends up damaging their own employees as well.
Fundamentally the union should be getting the workers a fair deal for their labour (conditions and wages); once the union starts interfering with the technical aspects or blocking labour saving investment it quickly sours the whole arrangement.