Do you have any evidence that open source code is lower quality?
The leaks of proprietary code, and the many examples of known security issues, the quality issues evident is most software, and the opinions of people who work on proprietary software all suggest the opposite.
I remember reading a study on source code quality quite some years ago, maybe it was featured on Slashdot. The result was that the lowest quality and the highest quality source code was proprietary, open source code was "pretty good but not the best". And that high quality proprietary code was stuff like operating system kernels and network equipment firmware, not business applications.