If Linux was on the desktop of everyone's grandmother, unpatched and unfirewalls, it would also be hacked in a jiffy.
Do you have any idea how stupid this statement is? First of all, such a statement simply assumes that it is not possible to write correct software. That is beyond arrogance and disregards the primary benefit of open source: like solid science, peer review is paramount in ensuring correctness of the results.

Furthermore, if your claim (that popularity of a software package somehow implies or introduces security problems) had any merit, Apache (the majority web server by a huge margin) should have been swiss cheese by now. Yet, somehow the minority IIS web server manages to have a serious remote vulnerability at least every year. How can you claim in good faith that popularity is what causes bad software, as opposed to e.g. proprietary development, or Microsoft?

Score:2, Interesting