I see this as Erickson doubling down on his dumb decision to disinvite Trump. And what a double down! He is not only fighting Trump, but he now dares Rush to pick a side too?! SRSLY?! There is no mystery as to how this will end up.
Clearly Rush will not 'apologize' for his treatment of "Trump phenomenon" or change his treatment of Trump on his program. Anything else would be like Trump apologizing for something he said. Erickson will find himself on an island. Trump and his supporters (this includes not only folks who will vote for him but also includes folks who favor others but who love how Trump has unapologetically defined the narratives for this election and shown that the eventual primary winner will come from the "fighter caucus") outnumber him greatly. If Trump won a spat with Megyn Kelly, a bout with Erickson will be a complete annihilation. The Trump phenomenon is anti-politician, anti-Establishment ... anti-Jeb/McConnell/Boehner/DC cabal (and this backlash 'phenomenon' is in fact their own creation/fault, a movement so sickened by their fecklessness, they dedicated to their removal from leadership) ... and fighting against it for 2016 is fruitless. The more you attack Trump, the stronger you make him.
If someone (Erickson or whomever) wants a different candidate than Trump to represent the "fighter caucus", they best figure out how to illustrate that their guy will be better than Trump without resorting to attacking Trump in the process. Treat it as a 'Shark Tank' competition ... beat him with better ideas, methods, marketing.
Or possibly ... even turn Trump into your biggest fan, investor and backer.