Couldn’t agree more but in the age of Twitter police and other judgmental mobs who live for their dose of daily outrage it’s somewhat challenging.
Also, just to point this out because it really irks me, visual design isn’t the same as product design. I’m somewhat bemused that people (even those who work in tech) still keep making this mistake in 2016. Product design is not just about making things look pretty. Ideally, that’s a part of it but making things easy and delightful to use is an even bigger part. And, as you said, content is also a huge part of it. Good product design is a combination of many things.
I do disagree with misspellings and using improper grammar making someone sound more authentic. I may not be representative of the population at large but that’s not the adjective that comes to mind when I see sloppy writing.