Is that saying not to use relativistic mass?

No! It doesn't say that. In fact that’s my entire point. It's only saying that one shouldn't use a velocity dependant mass. Notice that ratio p/v = p/c (since v = c for a photon) is not a function of speed. p/c for a photon is, by definition, the relativistic mass of the photon noting that for radiation E = pc we get m = p/c = E/c

^{2}.

Also, as I explained in the OP the value ratio gamma*m

_{0} = m

_{0}dt/d(tau) when evaluated for v=0 in a gravitational field where the gravitational potential is function of position does not have the value of m

_{0}. However m

_{0}dt/d(tau) is the relativistic mass of a particle.

Here's Matt Strassler's take on the subject.

http://profmattstrassler.com/2013/07/11/mass-ive-source-of-confusion/

Thanks. I'm (overly) aware of that position. He makes the same mistakes that Lev Okun makes in all of his articles. This is a very ignorant comment for a physicist to make. It’s blatantly false. He’s a particle physicist and they have no other use or application for anything other than proper mass so many of them have incorrectly assumed that since they don’t use it tat nobody else does either. A friend of mine, Alan Guth, uses relativistic mass in his thinking and in his teaching and he’s one of the most well-known particle physicists/cosmologists around!

He also makes the common mistake of confusing relativistic mass with energy. Consider the energy of a charged particle moving through a static electric field. The relativistic mass-energy is not the total energy that is conserved but only part of that energy, i.e. the kinetic energy + rest energy. It doesn’t include potential energy. If the frame of reference is not an inertial one but the components of the metric are time-independent. Then the frame has a gravitational field in it. Now consider a free particle (only inertial forces are acting). The time component of 4-momentum is what particle physicists call “energy” but that is not true for a particle moving in the gravitational field. The energy is the time component of the 1-form associated with 4-momentum and has gravitational potential energy in it. So his claim that mass and energy are the same is invalid in general.

Everything he’s saying there applies

**only** to particle physics and to nothing else. Beware of such people when they make such statements. They tend to think that they know what every single particle physicist in the world thinks. And that’s just silly.