It would seem that there is nothing derogatory about a statement of taste. To say, “I don’t like dry wine,” is a description of the speaker’s preferences and not critical evaluation of the wine.
Ostensibly, then, one should be allowed to say that he does not like the oratory style of a given lecturer. In fact however, such statements are generally prohibited, for they imply that he speaker lacks effectiveness.
Sefer Chofetz Chaim, 7 Tishrei, page 62