You can say... subjective, impressionistic feedbacks TEND TO MAKE Teachers react in defensive ways. Or even.. subjective, impressionistic feedbacks TEND TO CAUSE DEFENSIVE REACTIONS BY THE Teachers.

Although most commonly applied to "impressionistic art" you can have an impressionistic view of anything. If you were to do a google search you will find many examples of how this word is used in sentences. For many topics. Impressionistic = giving an overall impression rather than exact detail. The first corrector is therefore correct. I have voted her back up because someone made a mistake in voting her down. However the use of tend in the second part of the sentences is confusing and strange. Making it difficult to know what word is needed, I can only think to change the sentence like Tamara has suggested. "where did you find the sentence?"

feedback is an uncountable noun. Subjective feedback causes teachers to react in a defensive manner (react defensively). Or Subjective feedback makes teachers react..... Impressionistic is usually used for children or people that easily absorb other people's behaviour. It's not really correct (in my opinion) to use this word to describe anything other than people. Unless you are talking about a style of art. In the dictionary you can find examples of 'an impressionistic view' but as a 33 year native English speaker, I've almost never heard this.