You shouldn't prove someone wrong every chance you get.
John is a frequent participant on an online forum about Mechanical Turk where many people are not native English speakers and misspell words frequently.
John wants to help improve the quality of posts on the forum.
John offers helpful spelling advice to people who repeatedly misspell via private message.
John relentlessly corrects even the most minor of spelling errors by other forum members.
John is appreciated by other forum participants for his helpful advice.
John is greatly disliked by other regular forum participants and is seen as petty.