Actually, it might be fit to rephrase the argument to a new one, better tailored for the purpose of countering the "media narrative":
China has not obstructed FON in any way which would be consistent with being able to logically claim that its actions have demonstrated it has the potential to place civilian commercial shipping FON under any sort of threat.
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The truth is all nations have obstructed civilian FON in some way, if we want to expand the definition, whether it be within their own waters, disputed waters or even within international waters, and more often than not it is on the basis of national security.
For instance the USN stopped the Yinhe, a Chiese shipping vessel, while it was in international waters, due to suspecting it was shipping chemical materials to Iran (it wasn't), but despite this action we cannot logically claim the US is thus somehow a threat to civilian commercial shipping FON, because this is a unique action made on the basis of a nation's own national security and cannot be expanded to that nation's policy towards all civilian vessels or even all civilian shipping.
Similarly, in the case of commercial fishing in disputed waters, obstructing and regulating such boats are also unique actions on the basis of a nation's own national security and sovereignty and cannot be expanded to that nation's policy towards all civilian vessels or all civilian shipping.
Therefore, it is impossible to truly say "nation X has never obstructued civilian FON" because one can always come up with an example where it technically has. Thus, the rephrasing of the argument.