Was I wrong for doing this?

In one of my cles, we have an online blog where the teacher will post a discussion topic once a week, and we are to discuss it. For one of them, we discussed the Bush tax cuts and two of my clmates posted incoherent replies. I'm not referring to the misusage of words such as you're/your and it's/its, but rather the lack of proper punctuation marks and more severe spelling errors. I told them that while they did have valid arguments (they really did), their improper usage of grammar was distracting. One of them took offense to it and I apologized for the way he interpreted it and explained to him what I meant. Was what I did necessarily wrong? He was being a to me today, so I'm just trying to figure out whether what I did was really in the wrong.