One argument in favor of opposing them is that they will compromise cyclists' rights on the roads.
However, this does not actually seem to happen in many cases, though it does happen in some.
Wouldn't it be worth asking the question, for each specific case, whether or not any serious loss of rights would be likely to occur?
There may be people whose agenda involves getting bikes off the road; but they also seem to be in the minority. If an individual has had disproportionate exposure to these people, then that individual may well end up having an exaggerated perception of this as a problem.
Does anyone know how much of a problem this is? How strongly or widely or proportionately represented are these people in actual fact? And how often are they able to succeed in pushing their agenda (certainly there would often be opposition)?
There are many cyclists who prefer not to ride on roads. Perceived and misperceived dangers are factors in this; but there are other factors.
Some people dislike riding on roads because they find traffic distasteful -- noisy, unpleasant, smelly, litter-and-other-detritus-leaving, unhealthful and polluting.
Just as they would rather be riding on scenic backroads, they also prefer good, scenic bike paths. Few of them would picnic alongside a busy, noisy road. They would seek out an attractive, quiet park with trees and shade. The same impulse or preference is expressed in their choices for riding.
Many of these people simply don't ride -- or ride very little -- because they don't find the options that are available locally to be attractive or enjoyable.
Isn't getting people out of cars and onto bikes something that is worth considering here?
Also, rather than opposing the bike paths, couldn't alert activists be proactive in other ways -- acting to preserve or ensure (or even strengthen) cyclists' rights on the roadways, while at the same time supporting (or at least not opposing) added facilities?
Couldn't they be active in making sure that the process of building bike paths is steered or kept clear of the (unnecessary) adjunct tendency to limit cyclists' rights on roadways?