Hah, THIS would be some joke report, but if it really IS true, then why should we be respecting Microsoft after this
Couple of major things to keep in mind when it comes to those kind of comparisons:
1) 'Redhat' and its ilk also include bugs/patches for the application suites that accompany it, in addition to the core OS itself, unlike Microsoft does
2) Microsoft has fully admitted in the past that many of their hotfixes patch multiple vulnerabilities without fully disclosing this. Looks great in the graphs, 'only' one patch even though it really consists out of multiple seperate ones. this artificially lowers microsoft's patch count, something that the open source OSes can't/won't get away with.
And one more thing: if you look at the graph, you'll find that although Vista has a lower admitted vulnerability count, it has a significantly larger number of *unpatched* vulnerabilities than the supposedly inferior XP does.