It's not impossible to defend. Here's the former head of Microsoft's Windows division defending it easily:
I know that there are people in the industry who will agree with Apple on this.
a) Defending the industry's interests b) Defending US interests c) Defending capitalism
I'd say (c) is the highest calling for someone like Sinofsky. His worldview is that companies like Microsoft should be free to do what they want, as long as they play by (weakly regulated) US rules.
Europe's DMA, like China's Great Firewall, changes the fundamental rules of the playground and put in question the ascendancy of capitalist views and US interests.