You do realize that there are some people who don't care for grammar over the internet? When I was 8-10 years old I only cared for grammar in Language Arts class. Just cause someone doesn't use proper grammar or spelling doesn't mean they are automatically stupid.
As a general rule, if you don't care for grammar and etiquette, yes, you're stupid and not worth having around.
I generally only abandon capitalization at most when I'm either tired or trying to reflect my sheer awe at something's stupidity.