Don't take it to heart Brother.
I know the type of people. I used to be one. Grammar Nazis are what they are. Instead of addressing the actual issue, they just make a personal attack, usually implying the person is uneducated and has no place in giving their opinion.
Just pray for them. But, to help you out, you might try writing things in a word processor, and use the grammar check. I wouldn't worry about it on here, I doubt anyone would pick on you for it, but if you are posting on facebook or another forum, especially to those "intellectual atheists", then just run it through a grammar check
In Jesus name,
Luke