I think the main problem I have with this whole "shirtstorm" thing is that it feels as though I (as a man) am losing the freedom to wear what I want to work to benefit the sensibilities of women. Frankly, I don't own any shirts of the type that the man in question owns, and I doubt I would buy one. It looks tacky. But I do have a problem with the notion that the only way to solve the problem of the lack of women in STEM fields is to get men to surrender things. I feel you should have more freedom to wear what you want to work, not less, and this request for men to stop wearing slightly offensive shirts feels as though we are returning to the stuffy mid 20th century era when the only possible professional attire was a dess-shirt and tie.
In short, in my opinion the percieved benefit of having non provactive shirts does not outweigh the cost of being able to express yourself at work. Now, if someone were just being overtly offensive (perhaps having posters of hentai or some such posted all over their cubicle) that would be another matter. But a single shirt on the date of a major success for your organization does not strike me as overtly offensive. There's a gradient here, and I beleive we can allow professionals a broad ability to express themselves at work, without encroaching too much on the ability to be provacative.