Interesting comment. Once I went to a conference and met a Chinese postdoc from one of the best universities in the US. We went to dinner together and were discussing the talks in the conference. He made exactly this comment about one of the speakers, that he "does not know what he is talking about." I was curious and started to ask in detail why he thought so. After some discussion, it turned out that the postdoc didn't even understand the talk. He was simply trying to brag about the high quality of his own work (which it was) and was trying to do so by dismissing any other work that looked like could compete against his own.