There are three risks as I see it, and they genuinely are valid in all fairness.
The biggest risk, which I think is the one that has the CAA most triggered, is someone going out tomorrow, buying a drone and then flying it where they shouldn’t (i.e. over gatwick). That is a legitimate concern. This would also include those who we regularly see on Facebook or Reddit / Youtube who like to see ‘how far can I fly my drone’.
But only happen because of one of two things.
A. They are being malicious.
B. They don’t know the regulations and do so negligently.
To answer point A: It doesn’t matter what regulations are put in place, RID included, a malicious user will simply ignore them or circumvent them.
To answer point B: This is already mitigated mostly by geofencing. Assuming the [DJI] database is correct (which is something that the CAA could work alongside to ensure) The only drones that won’t be stopped with geofencing are the FPV / home built ones - which goes back to my point earlier, in that I don’t think there are that many people that would build an FPV drone or buy a RTF one that isn’t aware of the rules (and therefore wouldn’t fall in to this category). This is why I could see a valid argument being made to place a regulation on all retailers selling any RTF UAS to either enforce geofencing or at least have the user acknowledge that they are registered and have completed the minimum level of training.
The second risk, is that posed to people and property. But I really don’t think this is valid, as there is no evidence to backup the claim that drones are hazardous - particularly the sub 250g models. Certainly, they’re no more hazardous whatsoever than a kid playing baseball or football in a local park not to mention hazards posed by cars, dogs not on leads, or any number of other far less regulated activities.
The third risk, is to privacy. And this is the one that has the public triggered. The existing regulations (outside of the CAA, for example GDPR and data protection, trespass / nuisance etc) already prevent these so it is just a matter of policing. I suppose you could argue that RID would help police this, contrary to my point earlier about malicious users, as there probably are a small number of people out there who willing to buy a drone and use it to ‘spy’ on ex partners or whatever the case may be, but may not be willing to go to the lengths required to ‘hack’ and disable RID. BUT this is a very small minority of people, and should not be used to justify the implementation of RID.