I think it means if POTUS fires RR it equals media narrative will be he is being fired to block Mueller, or to set up firing of Mueller (as in obstruction of justice in the RUSSIA RUSSIA RUSSIA fake PROBE), and has crossed the red line (means a figurative point of no return or line in the sand, or "a limit past which safety can no longer be guaranteed)
Firing RR = block Mueller.
Firing RR = set up to firing Mueller.
Firing RR = Red line.