I agree with your statement, the thought of a hairy bloke stomping around the office in a dress is not a pleasant one. However, similar to the classic car, Drive It Day,
Where it only applys to the people who already own a classic, people aren't going to go and buy a classic car to drive it for that one day. The same would apply to Crossdressing Day. It's only really likely to be people that already crossdress or want to try it that are likely to get involved with it.
Katie