Because they have a perfectly fine position in the pipeline by promoting a framework for discrediting western media already; Dying in the hill of "China isn't doing genocide" or whatever is a rhetorical tact that would turn many people away. Let other people, especially those who actually have some familiarity with China and its media, handle defending China more competently.
"What about Israel/Palestine, then?"
There are definitely some rabid zionists, but generally among their audience Palestine is already strongly supported, which cannot be said of China (by which I mean that it's split, not negative). Virtually no one who is declaring them Hamas for their Israel coverage is that interested in what else they have to say anyway.