Normally I would let this slide, had I not just read the CNET report on Windows latest fix release for 14 security holes in doze, which makes 20 patches this month and also noted with interest that the average response time from MS from reported hole discovery to patch release being just over 200 days.
Strip back the FUD; apply the standard "there are security holes in Linux applications fixed all the time, but Gartner Group rarely complains about them, and if they do, it gets written off as anti-MS propaganda" "Windows" too, please.
IMHO, if you really want to be targeted by viruses, and walk around with a target painted on your back, go for it. Otherwise Use a different client.
I've been using Outlook Express for several years now. I've never once passed a virus onto anyone. Coincidence? I think not. If Linux had the market share that Windows had, then there'd be exploits found and abused in Linux. They might be fixed quicker, but anything we say about that hypothetical situation is mere speculation at this point. Yes, some of these viewpoints are exaggerated for this post, but just because some Windows users are a problem doesn't mean they all are.