If you want to argue that taxi protectionist laws are just, make that argument. "It's the law and you can leave" is, unfortunately, not that argument.
Morality is not black and white and two things you consider 'unjust' are not comparable merely because you can find a single word that you believe describes them both.
They are directly comparable in the sense that they satisfy the preconditions of Markoff's argument. My point is that if Markoff's argument were valid, then this crazy conclusion would also be true.
On the flip side, if that crazy conclusion is false then Markoff's argument must also be invalid.