Answer: the extreme emotions that he is feeling.
In this scene, Romeo confides in Benvolio, and tells him that he has fallen in love. However, he is extremely sad because the woman he loves does not love him back. Immediately after, Romeo notices that there has been a fight.
These events, all of which leave strong impressions on Romeo, cause him to have extreme feelings. This is shown by the oxymorons he uses in the text. He is confused and emotional, and believes the fight to have been caused by love, not hate. However, he cannot describe what love is, except through this series of contradictions.
Explanation: your welcome ladies and gents ;)