Fang Zhouzi should not have got himself in fighting with Han Han. Such fighting is inherently inconclusive. It may discredit Fang.
One may reasonably suspect Han's ghostwriting, but it cannot be PROVEN. It is not like scientific frauds.
For example, can you prove Cao Xueqin actually wrote <红楼梦>? Could Cao possibly possess such extensive knowledge and experience in all aspects of noble life, and even in Chinese medicine? However after all, does it matter if Cao was real author?
Fang's campaign against Han's ghostwriting is a mission impossible.