I agree with you on arboretum but "mustn't" is nice, that additional t just makes it look extra-fussy, like a weedy mustachioed fellow in a suit tut-tutting you, mustn't do this, mustn't do that, mustn't use the wrong salad fork

"The voters are stupid" isn't useful analysis or a political strategy. They will continue being stupid! You either need a plan to make them not stupid or a plan to win despite that