Hmm. Where is it implied that free software and proprietary code is incompatible? I do both as well, and I think there aren't enough people contributing to the discussions here who have a healthy respect for proprietary software. If anything, I feel that this perspective might help open source software to "grow up" in some sense or other.
The sort of code I write for business generally has very little technical merit, it's usually just webpages and the required code behind to drive them, the sort of stuff that is so boring and predictable that my eyes glaze over just thinking about it. On the other hand, I use open source stuff to do something that interests me personally. In latter, doing the work is its own reward.