Recent simulations of force-free, degenerate (ffde) black hole magnetospheres
indicate that the fast mode radiated from (or near) the event horizon can
modify the global potential difference in the poloidal direction orthogonal to
the magnetic field, V, in a black hole magnetosphere. There is a fundamental
contradiction in a wave that alters V coming from near the horizon. The
background fields in ffde satisfy the ``ingoing wave condition'' near the
horizon (that arises from the requirement that all matter is ingoing at the
event horizon), yet outgoing waves are radiated from this region in the
simulation. Studying the properties of the waves in the simulations are useful
tools to this end. It is shown that regularity of the stress-energy tensor in a
freely falling frame requires that the outgoing (as viewed globally) waves near
the event horizon are redshifted away and are ineffectual at changing V. It is
also concluded that waves in massless MHD (ffde) are extremely inaccurate
depictions of waves in a tenuous MHD plasma, near the event horizon, as a
consequence black hole gravity. Any analysis based on ffde near the event
horizon is seriously flawed.Comment: 9 pages to appear in ApJ Letter