I actually look at it a completely different way. There are so many users optimizing and digging into the core of open source versus proprietary that with so many randoms actions there's less "vulnerable" dark spots available. If we think there's a limitless X amount of vulnerabilities (since we don't know the true ceiling limit), open source will always be "X (vulnerabilities) - 1" compared to proprietary. Completely a math metaphor but gets the point across, It's a path that lessens the impact which we should be striving for over profit/monopoly motives.