No, it makes you correct. The author of this blog-post is confused.
The law of conservation of momentum in three dimensions only holds approximately, because classical physics is only an approximation. In relativistic physics, conservation of momentum hold exactly, and is four dimensional. The fourth component of momentum is energy, and the laws of conservation of energy and conservation of momentum are one law in relativity.
In Lorentz invariant terms: pμpμ = m2. [in a system of units where ħ = c = 1.]
In practical units and more familiar terms: 
]
As long as you can convert some mass -- usually binding energy from a chemical or nuclear bond -- into momentum/energy, you don't need "reactive mass." The article has been wrong since 1906.
There is nothing new here. Please move along.