Yes, this. It would be very stupid (and I think stupid is a fair term) for anyone with a medical condition with a timely need for medication to go out for any distance in the present conditions without carrying at least two, probably three, days supply of medication and, for a diabetic, food necessary to maintain their sugar level for at least two days (so a stack of Snickers bars or similar), and probably also sensibly water. People have to take some responsibility for themselves when they have been warned unambiguously that it is best to stay home.
In normal conditions if you go hiking up a mountain you wear stout shoes and take spare clothes, plenty of water, emergency food and spare medication in case you get stuck overnight, as it can happen. Those precautions are needed for *leaving the house* in most parts of the UK at present unless you're simply walking to the local shop. The conditions outside are basically the same as winter hillwalking except you don't have to walk up an actual hill.
The bus was however going too fast, as you have to assume there is a distinct possibility that another vehicle will unintentionally end up in front of you when on heavy snow/ice. My approach has been that (in my Land Rover) 20-30mph has been fine when well away from other vehicles or any pedestrians, but 10 probably nearer common-sense when there is something that could viably end up in my path even on the other side of the road.
Essentially you have to drive on snow and ice as if your brakes were completely non-functional (yes, I know you wouldn't actually drive were that actually the case). The bus was clearly not doing that - clearly a lot of skill was shown in the manoeuvre, but the manoeuvre should not have been necessary.