The source you cited was reliable about the Michael Graham and Chris Plante firings from WMAL in the past few years, so I have no reason to doubt this.
That station is going to lose market share. Who the heck is going to listen to amiable, inoffensive, namby-pamby Brian Niemann? They’ve tried other experiments, including the disastrous Bill Press, and nothing worked for them except fireball morning drivetime hosts. Conservatives like some meat in the morning.
But if that source is reliable, he wasn’t “yanked off” the air, he had himself removed because he wanted out of his contract so he could go run for office again.
The source further suggests that he may have purposely defied the station regarding speaking about Islam so they would HAVE to fire him.
I’ll say this — Grandy was extremely anti-radical-Islam on his show, much more than Chris Core ever was, more than even Michael Graham was. If he was trying to get himself fired, he did a great job of it and of exposing the radical islam problem to his listeners at the same time.