Pedestrians Only / No Bicycles

As I wrote in my previous entry, I encountered a "No Bicycles" sign this morning.
And then I rode the Big Woods trail this morning despite the sign that says Pedestrians Only.
During my ride I came across an older man hiking.

Basically, here's how the conversation went.
Man: "Are they calling that a pedestrian now?"
Me: "Excuse me?" (I heard something about pedestrian, but didn't quite understand)
Man: "Are they calling that a pedestrian now? The signs say pedestrians only."
Me: "Well,..."
Man: (man interrupts as he walks away angrily) "Yeah..."

I would really have preferred to talk to the guy than have him walk away in a huff. He looked like he probably hiked a lot, and it wouldn't surprise me if he was a member of The Friends of Webster Trails. It's not like he was some guy passing through throwing out jerky comments.
Of course I was breaking the rule so I expected someone might not be happy.

A couple of things frustrate me though. I haven't seen anything on the trail websites that tell which trails are for pedestrians only. The signs at the parking area didn't say anything about it either. It's not until I actually got to the trail that I found out.

I don't think I have a huge desire to ride the Big Woods trail in the future, but it might be a nice option. I'm guessing I'll find plenty more similar trails that I am allowed on.
What bothers me is that I don't see an reason to not allow bikes (and unicycles) on these trails. I could understand if the signs said something like "Warning. These trails are not bicycle friendly." Then families and non-advanced riders will avoid them. I understand why some limitations make sense, like not allowing motor vehicles on trails. They can be noisy and alter the trails. But why limit bicycles? If it's not to keep people from riding and getting hurt, then maybe it's because the hikers don't like having to step out of the way? Maybe it's because bikes move too quickly and startle hikers? Hikers startle me sometimes. Even when I'm hiking! That's just how it is in the woods.

I'm thinking about joining the Friends of Webster Trails. Maybe I can understand why the limitations are there, which trails I can currently ride, and maybe I can help open some trails to unicycles, if not bicycles.
I wonder how the hikers would feel if they encountered some trails that said "Unicycles Only"?