I'm torn on this issue, but I certainly don't think that whether giving out the code will decrease the chances of independent verification is a "bogus argument", and it's not about "protecting" anyone from anything.
Writing your own code for anything but trivial analysis is a huge time sink. If I can take someone else's code instead of writing my own, I'll do so. There is a very real chance that making all codes public will seriously increase overall consolidation and decrease independent verifications. (Independent verifications are a problem anyway because funding agencies are unlikely to fund redoing the same experiment and journals are less likely to publish them.)
Writing your own code for anything but trivial analysis is a huge time sink. If I can take someone else's code instead of writing my own, I'll do so. There is a very real chance that making all codes public will seriously increase overall consolidation and decrease independent verifications. (Independent verifications are a problem anyway because funding agencies are unlikely to fund redoing the same experiment and journals are less likely to publish them.)