Student's Criticism of teachers

Another issue- this time on my two week observation at Lambrick Park, where I will be doing my full practicum. My sponsor English teacher does not seem to be well liked by students. Some days I would arrive to the teacher's classroom before I got there, and kids would start bombarding me with comments about how they don't like this teacher, how students think hes racist, sexist, rude, a jerk, bla bla bla... I was absolutely stunned that these kids were openly sharing all this with me without me uttering a word. Now the problem is, I have to agree with the kids on some of the things they were saying, but I would obviously never engage in the conversation with them. How would I deal with this situation? I was terrified the teacher was going to walk in and hear them speaking about him, but at the same time wasn't sure quite what to say to them???