[burnerburnito]

What's he supposed to say? "Sweetie, you might maybe be possibly wrong maybe. I might be wrong too but i think it could be saying..."

He didn't attack you or act abrasive. You are right that "I think" is not supremely certain language, but it does actually carry certainty with it since you're not saying "I don't know anything about this, but I think..."

Conclusion: I believe you're being a bit overly defensive, and should relax a little. He wasn't personally attacking you, he was saying you were false when you were objectively false, without much in the way of personal insult or even arrogance, and cited his source reasonably well.