Why people don't think that things that they write/speak can hurt others?

well i was boring one ngày and i had the birthday 2 so i đã đăng in this club i have birthday today just because i didn't know what to do other and i get some các bình luận like this:oh happy fucking birthday (maybe he thinked i was an attention whore) and about 2 days later i đã đăng an another question: I know that this was đã đăng 1000 times before but.......post something funny....and they started to make irony with me someone wrote:
something funny (just thad he/she wrote just that maybe he was laughting with my sentences)
ok i agree my english spelling is not good but doing mistakes it help learning hoặc they used sarcasm like i was so dumb just please stop maybe people will use sarcasm again bạn maybe will say:ok girl when i will answear a câu hỏi in fanpop first i will see who is asking and than i will decide if i have to use irony hoặc not...I know that i am 2 sensitive but PLEASE stop!