Subjectivity can be exploited to write content that provokes. Nor do you have to play fair when you write. However, there is a fine line between provocation that engages and provocation that alienates.
In critiquing, the subjective aspects of the work and your subjective reactions can give you insight into how a piece works. Being reactive is normal, but an effective critiquer also need to assess from whence a reactions come from, separating the personal from the universal.