I have never attacked anyone for their grammar on a forum

I am proud of that. I really don't understand why people do it either. My best guess is that it is a way of saying " I am better than you". Its kinda like an interview I saw where Bill O' Reilly was interviewing Donald Trump. Donald brought up the Great Wall of China and used it as an example and justification for both the plausibility and the necessity of building a walled border.

Bill O' Reilly side stepped Trumps point and asked Trump if he knew why the Great Wall of China was even...

I have never attacked anyone for their grammar on a forum