I agree that unless there is good evidence, it is no good making baseless accusations against the GB of this kind. At the same time, the idea that it may be possible that GB members have been involved, is not in itself terribly implausible. There are a few differences from the idea that a Russian spy may be on the Governing Body, for example.
1. Abuse is depressingly common in society in general whereas being a Russian spy is not common. So on a purely statistical basis one is much more likely than the other.
2. Religious organisations of all kinds have concealed abusers at high levels. If JWs are unaffected at the top, then it would mean the leadership is better than the general JW membership (which has had around 1 per congregation, according to some indications, such as the Australian Royal Commission) and better than other religious groups.
3. The WT has actually stated in their literature that abusers have been prominent in the organisation.
4. Greenness was removed from the GB but was not removed as a JW, and was allowed to continue in local congregations.
5. Their own policies and actions indicate that reputation of the organisation is more important than almost anything else, so that if such a case arose it seems plausible they would do whatever they could to conceal it.
So while it's irresponsible to accuse the GB unless there is good evidence, at the same time it’s not unreasonable to be open to the possibility and open to any evidence that might arise. More reasonable than expecting Russian spies to be uncovered on the GB, for example.