The Apple brand is one of the company's greatest strengths, hard earned over decades. Steve Jobs helped launch the company, eventually found himself banished from it thanks to what was merely standard business practice at the time, and then returned as the prodigal son when the business experts in the boardroom had failed to turn things around. Apple nearly went out of business, probably more than once during those Jobs years. It used to be a minnow in the great tech pond. It was really up against it.
We all know (don't we?) how things moved on and upwards for Apple, on a global scale so awesome that the Apple brand has since become a benchmark signifier culturally. Not a bad result for those guys in the garage and all us Apple customers who 'got it' – those customers buying their Apple IIs, Lisas, and on down through the years before Apple became as much a fashion to many as it was tech company. These days, thanks to the Internet, everyone's an expert but of course not everyone can see the bigger picture (or even the detail) – because their vested interests obscure the view.
So for Apple to have achieved all that progress and commensurate success, and then for others – well-meaning consumers and, less so, politicians and competitors – to expect the company to allow a profound dilution of those very strengths that makes Apple what it is, by initiating third-party interference and the inevitable undermining of the brand and user experience (and that's what will begin to happen were sideloading to be imposed), makes little sense, certainly not to Apple, and not to this consumer either. I buy Apple because it's Apple. I know what I'm getting and it suits me very well. I'm willing to pay a premium to get it and it's worth it. There are lots of other choices that I could have made. I've made mine because Apple's is a compelling case and gives me what I want and rely on.
For those Apple customers who don't know nearly enough about their devices in the way that seasoned Apple purchasers and 'fanboys' do, they've simply hit lucky with their (less-informed) choice of Apple computer, phone, etc and will benefit regardless of how aware they are of the merits of their choices and what provides the technical basis for these merits. A diluted version of Apple will not be helpful to these people either.
Apple does not have a monopoly. It is a competitor with its own unique attributes, long developed, well worked and in many ways superior. Thus it has established itself as the global company it is now. Unfortunately, everyone wants to take a shot at the champ. It's human nature and it's probably always been like that. It's not always appropriate though, and so called experts might do well by reminding themselves of the bigger picture. Take away a bit of what makes Apple great and ultimately we might not be left with any of what we actually value about Apple.