I fully agree, but I have to admit, I have made every single mistake that I hate. When I am thinking about the idea and typing fast, I can break any of the rules that I hold dear and judge others on. The one that hit me the hardest was when I wrote ‘then’ when I meant ‘than’. (I reserve particularly harsh judgement for people who make that mistake.) But I’ve also actually written ‘could of’, and every possible iteration of ‘their’, ‘they’re’ and ‘there’ in the wrong context. I have edited for a living for decades. Editing and writing are two different things.
Like I said, I am typing fast and thinking about the ideas. When I do this, I am typing out the words partly based on how they sound. It’s not time for grammar, it’s time for getting my ideas into the computer. That’s when it happens.