Proper spelling and grammar is going to be a huge bonus once you go to college or start looking for a job...
Last year at college, a friend of mine wrote a 15page paper about rock tectonics in western France and got sent back home from his presentation because his opening page contained a spelling mistake ....
Or lets say you're an excellent carpenter and you're applying for a job somewhere, and your résumé starts with a huge spelling/grammatical error, even if your credentials are very good, you're gonna come off like retard and probably miss out on the job because someone else wrote without errors ....
So if someone shits on you for bad spelling/grammar, try to learn from the mistake and i'm sure you'll thank him/her/them later .....
That being said, i'm Belgian, i don't speak English for shit and it amuses me when i can correct Americans/Brits/Canadians on spelling or grammar mistakes, it gives me a raging boner !
:)