They call this a "bribe" because there seems to be this assumption that open source developers write code purely out of the greatness of their heats, that this is the status quo, and that adding a financial incentive towards fixing bugs is morally wrong.
The biggest problem I have with a ton of open source software is that the really big issues (particularly usability, but even features to make some software on par with their proprietary counterparts) are either hard, boring, or both. Coding functionality like tables you can resize with your mouse like you can in MS Word, isn't as much fun as writing a Personas feature in LibreOffice to let you use Firefox personas in the UI.
People who code for a livelihood aren't guaranteed to make better code than open source developers. But they are motivated to do the messy shit to solve end-users issues, because there's money on the table.