Because the parent poster suggested they in fact wanted to open source more stuff but couldn't for these reasons. Therefore, it is a strong case against.
Maybe we're using different definitions of "strong case", I'm imagining it in a court of law, a case for going one way is "billions of dollars and market dominance" - that's a strong case. The case for changing direction is "in 30 years, giving your stuff away will be less legal trouble". That's true, but it's not a strong case for changing direction, it's a minor shrug. Strong meaning enough to overturn the competing arguments and push a different decision, not just "isn't wrong".
