Factual error: In every scene where knights collide on the lyst, you see their lances in one hand and the reins to their horse in the other. When knights jousted, they would drop their reins before impact so that a severe impact would not cause them to jerk the reins or become entangled in them causing more damage to themselves or the horse.
Factual error: Worth mentioning, because we see it written on screen: in French, Jocelyn is a man's name -- even its pronounciation is different. For it to be a woman's name, it has to be spelled Jocelyne.
Factual error: Ulrich's armor repair is either gas welded or arc-welded, not Forge welded. Forge welding is the only type of welding available at the time and is usually extremely different if even noticeable. (00:35:10)
Answer: The reason he is so agitated has to do with the manner in which he won the tournament. If you'll recall, William states, "I'll not be champion until I beat Adamar." Adamar had forefeited beforehand, (not wanting to joust against royalty) therefore not giving William a true victory. After his half won victory, Jocelyn's (Shannon Sossamon's character) inane chatter just rubbed him the wrong way. It had nothing to do with what she was saying...if anyone had spoken to him he would have reacted in the same way.