The unicycle can be considered something impractical and suboptimal almost uniformly. You can't go fast, you can't carry anything, there's no way to give a friend a ride. It is perhaps equivalent to a person not developing their body in a way that makes them a useful citizen/comrade/etc.
The response from men seems to mainly line up with how we'd react to such a thing in evolutionary context. We instinctively realize that unicycle ridding isn't a value-add to either the rider or society - both are less capable than when a more "appropriate" vehicle is used (we have "standardized" on bikes rather than uni-cyclers or trikes because those are clearly superior across almost all non-circus applications.)
Men react as they do because intrinsically we want society and its members to be stronger - as we shoulder the load of those who aren't. So there's sort of a "hope" that enough of these remarks will encourage the person to get their shit together.
Women are more focused on comfort - so they react the way they would to seeing someone physically weak and less capable than the average person - with kindness and almost a pity. I don't think they are lining up to sleep with him.
Obviously these are not exactly "helpful" reactions to someone riding a unicycle around the park but the underlying drives are still roughly right. A nation of unicycle riders is going to get conquered.