Earlier quoted context omitted.
I think of it like the UN. You may not like the USSR (the creators of the UN certainly didn't) but if you don't give them a seat at the table the whole endeavor is useless. Microsoft is by far the biggest contributor to .NET in general, and the .NET foundation projects in particular. No organization can purport to have a say over the evolution of .NET unless Microsoft has a seat at the table.
The comparison with UN is weird, UN does not have 1 member that is super special. Anyway the issue seems to be that the messaging does not match the reality, MS needs to be transparent and very clear in this, then projects can decide if they agree with the conditions. Java world had from a long time foundations that were independent of Sun/Oracle.
I think there is still the fear of something like this happening with .net if anyone ships with a modified version or reimplements a piece to meet their own needs, at least from chatting with my developer friends over coffee.