Although using 'correct' grammar is an important part of writing, I don't think that anyone here - especially me - claims to be an English expert.
After all, if that were the case, we would be tearing apart the 'American' spelling of English words such as COLOR (correct spelling: COLOUR). Admittedly, this is a pet peeve of mine but since all programming languages and most documentation I've seen have used these, I just sit back and use what's there while I quietly grind my teeth.
Now to the point:

• As long as the document can be easily understood without a lot of ambiguity, we should leave any grammatical errors as they are.
• Be thankful,or at least appreciative, that there is a tutorial around to help those who need it.
• If there is a serious problem with the grammar, simply /msg the author and explain your concern.

This is just my opinion but I think that we can be much more productive and helpful to one another by letting a few little grammatical errors slide.