You really can't believe that people purposely use bad grammar and misspell words just to be rude,can you?
They may not do it
just to be rude, but that's the result, nonetheless. Rude behavior doesn't necessarily have to be done on purpose, it only has to be done without regard for others.
Ever pass someone on the Interstate only to have them utterly destroy your night vision by flooding your rear view mirrors with high beam lights to let you know you've missed 'em and it's OK to come back over? Same thing. Very few people do that
just to be rude. Some do it out of laziness. Most do so out of ignorance. And it's rude and inconsiderate, regardless.
Proper grammar and perfect spelling isn't likely to happen on an informal forum such as this. It's not necessary, as long as your post is comprehensible. Paragraphs, semi-properly constructed sentences, things like periods at the end of a sentence would be nice, maybe a capital letter at the beginning of a sentence, even an improperly placed breath comma would be nice in some cases.
If your post in unreadable and incomprehensible, not only is subjecting readers to it and expecting a coherent reply rude and inconsiderate, it's self-defeating. If no one can understand you, no one is gonna take you seriously.