The UASF non-mining node army is ostensibly what pressured the miners into bending over and accepting Segwit. So history has shown that they can indirectly provide benefit, depending on what you'd consider a benefit.
That is certainly a possibility. Why miners would bother listening to what a sybillable agglomeration of entities that have no demonstrable relationship to economic power is an exercise in understanding delusional stupidity. But there it is.
So yes. In at least one instance, it has been demonstrated that a detriment can be foisted upon the network by PoSM. But in no way was this demonstrative of
forcing a benefit upon the network via the
power of non-mining fully-validating entities.