#2 massively ignores the fact they didn't bother to solve the problem until much much later. In fact, everyone else solved it the same way as Microsoft before then even on Unix. Actually, a bunch of Unix guys were involved in the design of UCS-2 and UTF-16 so I'm not sure why it's Microsoft's fault.
But yes, some Unix guys eventually faced with a bigger problem, significantly more time, and a design already started by the Unicode Consortium eventually solved it better. But that's not really much of an argument.
Also arguing that there is no risk going to UTF-8 is ridiculous. Anything that treats UTF-8 as ASCII, as you suggest, is going to do it wrong in some way. At least making a new API forced developers to think about the issue.
But yes, some Unix guys eventually faced with a bigger problem, significantly more time, and a design already started by the Unicode Consortium eventually solved it better. But that's not really much of an argument.
Also arguing that there is no risk going to UTF-8 is ridiculous. Anything that treats UTF-8 as ASCII, as you suggest, is going to do it wrong in some way. At least making a new API forced developers to think about the issue.