No, my argument is Apple should not be in control of MY device. A car company should not be able to choose where I can go or what things or people I can have in my car. A housing company should not be able to decide who can I have in my house or what companies I can shop for furniture and/or decorations. A refrigerator company should not be able to decide where I can buy groceries or what things I'm allowed to store in my refrigerator. And, a computer company should not be able to decide what content, including apps, I'm allowed to put in my computing device.
If you want safety in any of those situation you are free to choose at some shop you trust but no company should be allowed to limit where I shop.
You claim there are good and valid reasons for a closed system. I claim those reasons are invalid and/or immoral. In an open system you can choose better stores. In a closed system the better stores are banned. To take one example, Real Chrome is more secure than Safari. This is provably true by reading the CVE lists. They have about the same amount of bugs but Chromes bugs have 7x less "arbitrary code execution" than Safari. But, I'm not allowed to run a more secure browser on iOS. Another example is the Hong Kong app that Apple banned. Apple has no requirement to carry any particular app but it's immoral IMO for them to control the phone itself such that such important apps can't be installed in other ways. Yet another would be sexuality apps. Apple censoring such apps is arguably as immoral as banning LGBT people from anything.
Apps are speech as ruled by the Supreme Court, and there are plenty of topics that are conveyed better via an app then a book/video but Apple's banning of apps means that while they allow you to download sexualized books and movies they don't allow you to download sexualized apps. That's a severe form of repression and is immoral