I'm going to fail at completely or concisely summarize the plot of Blazing Saddles here.

In the movie, there is a deeply greedy railroad tycoon who wants to build a railroad through the desert. The best place to run the railroad through is already occupied by a town of white settlers called Rock Ridge. Meanwhile, a black worker on the railroad becomes both popular and uppity. The harebrained scheme to kill two birds with one stone: Appoint the black man sheriff of Rock Ridge. So the tycoon is relying on the townspeople to be useful idiots and lynch the black man, while simultaneously expecting the insult of a black sheriff to drive the town into chaos so he can break up the town and run his railroad.

There is a scene where the black man, in his capacity as sheriff, greets a little old woman saying "Mighty fine mornin, ain't it?" She responds "Up yours, N***er!" Upset at this, his friend (a former gunslinger turned drunkard, played by Gene Wilder) to try to cheer him up, saying "these are people of the land, the common clay of the new west." Gene Wilder ad libbed the line "you know, morons." which caused Cleavon Little (playing the black sheriff) to genuinely laugh, which made it into the final cut of the movie.

Shenanigans ensue during which a man named Mongo punches a horse to the ground, then Madeline Kahn happens, and it comes out that the tycoon (and the governor in the tycoon's pocket) is trying to hurt the town and the black sheriff is actually on their side, the townsfolk learn and grow as people and put aside their bigotry, in the words of the mayor "We're okay, with the ners and the cks, but we DON'T WANT THE IRISH. Ah, prairie shit. Everybody!" meanwhile the tycoon and his cronies are mainly driven by greed and unable/unwilling to grow, accept others or find equitable solutions, and are defeated/humiliated.

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So in this context, calling muslim Americans who would vote for the Republicans because the Democrats are in office while Israel is going full Nazi is calling them useful and disposable idiots. Which is exactly what they are. The Republicans actively want to kill muslims. Muslims are black people who aren't even Christians, the Republicans would exterminate muslims recreationally. They'll gladly take their votes though, anything for more power. Meanwhile the muslims be over here talking about "The Republicans hate women and jews, I hate women and jews; it's like they get me, you know?"