All public resources must be managed. They cannot be managed
to please everyone. Hiking trails are best managed to please just one group –
hikers! What’s the matter? Can’t walk?

Why must they be managed purely to please hikers ? How on earth do you justify that ?

We have all seen trails that have been ruined by mountain
bikers. Mr. Vandeman is the expert on that subject.

I have jousted with Vandeman several times. He writes nonsense and he has, in alt.mountain-bike, admitted actions that, despite all his protestations, show that he was correctly convicted of battery. I tried debating in a reasonable fashion with him but his inane conversation inevitably degenerates into calling everyone liars when they point out the gaping flaws in his assertions or logic. If that's your 'expert' I suggest you find a better one PDQ.

ERs are being flooded with injuries and fatalities from
mountain biking on hiking trails. If you had even an ounce of common sense you
would know how dangerous it is. Some extreme jerks are even encouraging children
to take up the sport.

Do you understand maths ? If there are close to 50 million people riding in the US then, even for a very low risk activity, there will be a fair number of injuries and even some fatalities. However, statistically, the risk is way lower than driving ... and is also way lower than dying of ischaemic heart disease which is an order of magnitude higher. Bottom line, you are far LESS likely to die if you take up mountain biking as opposed to sit on your butt in front of the TV.

Even if it were possible, I would be against it on esthetic
grounds. Mountain biking is a sport, hiking is a religion. The two things don’t
go together.

Says who ? This is an assertion without any factual backup. I accept that it is what you feel ... but feelings are not normally valid reasons to take policy decisions.

I have a mountain bike myself which I ride on the gravel roads
hereabouts. Minnesota has thousands of miles of such roads and are ideal for
mountain bikes. Mountain bikers are hardly ever are in a* position to
appreciate nature. They are always going too fast. You have to go slow to
appreciate and to consider nature.

Two rebuttals. 1. As long as they don't hurt anyone else, it is not for anyone to determine how others enjoy nature and, 2. Mountain bikes go slowly uphill and stop periodically ... giving ample opportunity to enjoy the environment.

It is brute reality. Get used to it. We hikers hate mountain
bikers on our sacred trails. Get your own trails and stay off of
ours!

It's YOUR reality. I very much doubt there are too many others who feel that way. It's as inapplicable to the overall situation as my stating that, where I live, hike and ride there is no animosity. It's a personal experience; what evidence do you have that others share your hatred ?

And, even if they did, such emotional baggage is not valid grounds for making any kind of decision. That needs cool heads and logic ... not emotive rabble rousing.