If FreeBSD, OpenBSD, NetBSD, RedHat, Debian, SuSE were packaged and and sold in stores, how would this be any different? Oh wait, They are packaged and sold in stores!
Just by comparing the OpenBSD security track record to the one of any Windows release would dismiss your point.
People find remote exploitable flaws in the aforementioned OSes during during their pre-release, release, after-release, alpha, beta, gamma, delta force, and nuclear reactor stages.
It´s not black and white, while no OS is perfect, there are measurable differences on how much they are exploited. Diversity would make trojan/virus writers job harder. So diversity is good.
No one's perfect, not ISPs, not users, not software vendors, not you. So please stop telling us about the lifestyle on planet Utopia.
So by telling people to shut up you expect to make the world more secure? Right :) Pete