Trump didn’t say anything about Walker, AFAIK, until now after a Walker person called Trump “dumb dumb”.
Walker ought to fire him or have him apologize.
Unless Walker wants to go against Trump, like Perry, Graham, Bush, rather than use Trump, like Cruz, Fiorina.
The fellow is a fundraiser, not staff. You don’t”fire”your fundraisers. In fact, you try not to annoy them.