The sentence talks about those who are wary of insincerity. To them, a great compliment will be something of negative tone. They would ideally be too wary of a great compliment.

Now, looking at the answer choices, acclaim and repetition are out because of non-negative tone. Among A, B and C - malice is too strong and hence "great malice" will become too negative. Between A and B, scrutiny makes lot of sense. 'Great obstruction' is not in line with being wary but 'great scrutiny' is.