Show me where I said we should accept their use? That market needs intervention to stop it encouraging use of all sorts of illegal vehicles. Targetting the illegal motorbikes will probably see some switch to illegal car driving instead, which is less obvious a target but a far bigger threat to others.
At present, there's greater attention paid to illegal motor vehicles on the road than illegal use of what many claim are bicycles. However if on-pavement use, in pedestrianised areas is causing problems, then they have to act.
Oh that's almost cute! Short-term crackdowns are not general enforcement and so people will still not estimate that the risk of being caught is high. Also, if the crackdowns are primarily on e-motorbikes, it will seem to some that any car is a good move, whether or not they are insured to drive it or even hold a valid UK licence: anything that doesn't ping ANPR will be good enough. An illegal rider with a branded cube backpack is pretty visible and identifiable, an easy target. Illegal drivers with cubes in the footwells are much less obvious.
Things should be restructured to remove most incentives to use the illegal bikes. As well as intervening in the takeaway market, government should be setting traffic lights to give green waves at legal bike average speeds (so faster ones get red lights, which need policing anyway) and things like that.
The thing to remember is that many see them as legal bikes, with electric assist. Official classification is a Light Moped, not motorbike.
Not as easy identify as you claim. Working on your delivery rider proviso, you're identifying the backpack, not the rider or vehicle. The illegal e-bike and rider will have very few means of identifying them. At present there's an increasing number of taxi and private hire drivers doing deliveries. Doing this whilst carrying fare paying passengers isn't covered by their operating license or issued plate. Illegal but they're on the road legally.
Why should we adapt to use of illegal use of a vehicle, to allow those travelling faster the ability to continue to flout the rules. How many riders are riding at the faster average speed. Overall the average speed on a bicycle isn't that high, due in part to the roads we share with other vehicles. There's times I'll be faster, times I'll be slower than other vehicles on the roads, due simply to other traffic.