Accepting the risk or banning the activity are rarely the only options. In most areas, the answer is to control the risk.
To use the driving analogy, we have various rules and speed limits; speed limits are lowered where pedestrians are likely to be around, road layouts adjusted, and so on. This doesn't remove the risk completely, but does reduce it to a level that people find acceptable.
In this instance, it seems reasonable that someone could perform a risk assessment that overlayed the proposed display sequence over the terrain and identified potential areas of higher risk (such as a high-energy manoeuvre performed directly above a major road). Having made that assessment (or studied it if performed by someone else such as the pilot), the FDD is then in a position to assess whether or not the risk is acceptable, and if necessary what can be done to mitigate that risk. The point made by the AAIB is that there appears to be no evidence that such a risk assessment was performed by anyone, in which case no-one would have been in a position to determine whether or not any risks were acceptable, or to consider what steps could be taken to mitigate them.