It was most definitely unfair. Instructing him to "go back" to school assumes he's been to one to learn English in the first place. There's a general disdain here for foreign posters that I find quite disgusting. You'll also notice that so-called "grammar nazis" are usually quite inept themselves.
Bend3R, you would be wise to use grammatically correct sentences when criticising others' writing and adopting that patronising tone.
http://hlds101.com/
There should be relevant resources written in your first language, but you neglected to say what that is and you would probably achieve better results searching for them yourself.