I don't think that the line between "I disagree with your opinion" and "I think this is incorrect" is always clear, particularly when new theories or analysis is being floated. As examples:
If I state that "chocolate is better than vanilla", and you disagree with me, it's not really that you think I am incorrect; you simply just disagree with me.
However if I state that I think "[country] will do [something] in Crimea", then you might disagree with me because you do think that I am incorrect. However in that case, because my statement was speculative, there isn't a strong sense of "objectively correct or incorrect".
I think that most 'disagreements' in online conversations are closer to the second than the first.
If I state that "chocolate is better than vanilla", and you disagree with me, it's not really that you think I am incorrect; you simply just disagree with me.
However if I state that I think "[country] will do [something] in Crimea", then you might disagree with me because you do think that I am incorrect. However in that case, because my statement was speculative, there isn't a strong sense of "objectively correct or incorrect".
I think that most 'disagreements' in online conversations are closer to the second than the first.