Of course, drunken rants and those that use English as a second language are exempt from scrutiny.
Here's the thing, knowing the difference between their, they're and there is elementary school stuff. The same goes for lose and loose as well as dozens of other commonly misused words and phrases.
Elementary School
So when someone doesn't use the terms properly, it either means that they are ignorant of grade school skills, or they are so self absorbed that they feel their time is too valuable to waste on taking a moment to make sure proper grammar has been used.
I would also like to point out that there are medical conditions which cause some people difficulty. However, these are rare enough to be excluded from this conversation.
Anyway, I see no need to score someone based on their ability, or lack of, to utilize the language.
Just don't get pissy if I pull out the Grammar Nazi card on occasion. (It's quite rare after all.)