In my view the ability to structure communications is important. I don't think that's the same as being a grammar nazi. For example if you have a zero tolerance policy for it's vs its, or for commas making things confusing, the framers of the US Constitution would fail the test. Not only is 'it's' is used as a possessive but try to parse this:

"No Person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any person be eligible to that Office who shall not have attained to the Age of thirty five Years, and been fourteen Years a Resident within the United States."

Yet I doubt we would doubt the authors' intelligence, creativity, and professionalism.

The simple fact is that grammar mistakes and grammar of non-standard dialects is one thing, but an inability to structure an email or other communication is a much bigger deal. You can't fault the guy who learned English as a second language, whose native language has no gendered pronouns and gets confused all the time, and the same goes for non-standard English dialects like AAVE.

So that's where I'd draw the line.