TBF there is a considerable difference between 1981 / 2011 and this - mainly in terms of how much it was aimed at a particular community / perceived members of that community, and secondly how (if not pre-planned it was then) much the ground had been prepared for it in advance (via the media, social media, commentators, influencers / grifters, various politicians and so on).
I agree that sentences pour encourager les autres are not always the best way of dealing with "normal riots" (especially because the people hit hardest are usually the most remorseful, or are shamed into handing themselves in by friends/family) but this had much more of the flavour of a pogrom, and I think a message has to be sent that reminds everyone how this will never be tolerated. Obviously to do that properly then they (HMG) need to go after those at the top with appropriate measures, not just hammer the idiots who physically did things.