If someone stereotypes your city (gay and weed references) and you don't like it, then don't respond by using stereotypes about their city (rednecks, religious references).
That being said Des Moines is far from a horrible city, in fact given the location, climate and local resources/economy, Des Moines is actually quite impressive. It is decently sized (not big, yet not tiny), relatively low crime, it's clean and white collar, well educated, and has an impressive skyline for a city of it's size.
Your stereotyping of Iowa is quite wrong by the way... Maybe you could say that we were Bible thumpers, anti-gay and anti-weed a few decades ago but the digital-age of the computer and the presence of cable and satellite has brought the entire nation to a relatively equal level as far as trends go. Your generalization of calling Iowans rednecks could not be further from the truth as we are one of the most educated states that votes liberal quite often (although personally I am disappointed by this...) and Iowa is probably one of best states in the nation when it comes to civil rights, aka gay marriage (although I believe money was most likely the driving force behind that decision).
Would you be mad if I characterized Denver as a bunch of atheist/agnostic pseudo-intellectual, hipster, brainwashed Fabian socialists who worship Charles Darwin as a God? You probably would be pretty mad if this was my actual belief, but based on stereotypes, this is what one would conclude about Denver and most of Colorado.
I'm guessing your hatred for Des Moines stems from the climate and lack of geologic features surrounding the city, then it does from the city itself. This is why Des Moines is never a place where I would want to live, but only because of cold weather and lack of interesting geologic features such as mountains or an ocean, but not because the city itself. Des Moines is a fine little city given all the disadvantages surrounding it.