Why does derrington break up with massie in sealed with a diss?

Derrington breaks up with Massie because he has an "issue" with her. Massie finds out of his "issue" with her using ESP. Later, during Skye's end of the year party, Derrington tells Massie that his "issue" with her is that he thinks she is immature. He says " I'm into older women now ", reffering to some eighth grade girls he was hanging out with.