You're going to need to give a much better reason than "proprietary" to discount the VB argument. There are lots of good ones, but this isn't one.
Proprietary isn't just a matter of whether the language is well-supported or not, but where it is supported.
For example, say you've spent several hundred hours of your life learning Visual Basic, and then several thousand more hours writing the Great American Program, in Visual Basic.
Now your boss wants you to get your program running on a Mac. Or a Unix box. Or a Linux box. Or anywhere that isn't Windows.... and here's where you find out that it simply can't be done, because Microsoft doesn't support anything other than their own OS's.
So, all of the time you spent learning and programming with Visual Basic gains you nothing at this point; now you have to go back to square one, learn a different (hopefully less proprietary) language, and rewrite your program from scratch in that language.
That's the real problem with "proprietary". You're locked in to doing only whatever your single-source vendor wants to allow you to do.