I judge people in this way. So do many others. It's human nature. (And it's my job.)
Are you willing to let your typos and grammar errors be the standard by which you, as a human being or as a business owner, author, or educator, are judged? Are you a great storyteller of history, romance, spirituality, or intrigue, but are not as skilled in proper language conventions?
You've sweated the hard work over weeks and months (maybe years) of writing a book, website copy, or classroom syllabus. Don't release or publish your work until a skilled, experienced editor has reviewed it and you've revised it based on professional recommendations. I'm a professional editor, and a darned good one if you believe my
clients' recommendations, but I have always relied on that last set of eagle-eyes to alert me to what I missed when caught up in my own creative process.
There's far more to "editing" than proofreading. More on that in another post, another day.