Hmm… To be blunt, I really don't think you're understanding much of what you're criticising here… I'll see if I can explain.
Er… okay… honestly, I'm not sure what that clip has to do with anything you're saying… but we'll come back to it.
This has recently frustrated me. Has anybody been through this?
What has frustrated you? Been through what? The video (or whatever you see in it)? Or the idea of "bashing your uke" that you mention in the title? Reason I ask is that the two aren't really the same thing… in the clip, the "uke" (it's not a Japanese system, so that term isn't correct or accurate…

isn't being "bashed"…
You do a demo your instructor tells you exactly what to come at him with. He knows when you are going to throw and you are not really fighting back. Then he springs on you a hundred miles an hour with solid finishing shots and spazzy submissions.
I'm going to give you the benefit of the doubt, and assume you meant to type "snazzy" submissions here… but, more to the point, yeah… that's kinda how a demo works… the "attacker" comes in with the prescribed attack (well… most of the time…

, and the "defender" responds. Of course, the context, and tactical expressions dictate (at least in part) what happens next on both sides… and yeah, it can involve "fighting back" in some form… but, in this instance, one of the basic tactical methods of Krav Maga being demonstrated is to completely overwhelm the opponent… to not give them the chance to continue to attack, or to really fight back at all… just to "duck and cover"…
You might note, of course, that absolutely none of the shots in the clip were landed "solidly"… nor were there really many forms of submissions, regardless of poorly chosen descriptives… I agree that the pace of the response should match that of the attack, but that's about it.
It is not neccesary. The idea of a compliant demo is so people can see what is going on.
No, that's one potential idea/aim of a compliant demo… it might just as easily be to impress others with a display of athleticism, strength, precision, speed, aggression, or anything else… or to highlight tactical and technical methods of a system or teacher… or to entertain… see if you can figure out what the clip's purpose is…
I would have thought that people accept that it is not real life and not resisted so take a chill pill and just show the movements at a casual rate. It is not like the uke is going anywhere.
Why would they do that if the purpose is to showcase aggressive, overwhelming responses? This is kinda what I was getting at when I said you don't seem to be understanding what you're critiquing…
If you do want to show technique at a million miles an hour then do the drill resisted. Give the other guy a chance to make you look stupid by defending.
Uh… no. Resistant drills are one thing, prescribed responses are another. And yes, if you want to ensure you can respond properly with the prescribed responses, you need to do them at proper, full combative speed. To suggest that you should only do them "chill" is really rather, well… I'm trying to find the word… stupid.
Thing is, why on earth would you, when demonstrating the system you train in, want to be made to look stupid? When training, testing etc, sure… but in a demo? That's so far out of whack with the reality that I hardly know where to start… besides which, let's say it's me doing the demo, if I'm working with someone, and they suddenly start coming back with something "out of the script", then I'm going to respond off-script as well… which firstly defeats the entire purpose of what I was trying to demonstrate, and secondly, is not going to be a pleasant experience for anyone.
My two major problems with this. One it is just not cool. You are playing at two different levels one going easy and one going hard. You can't work like that. One pace is only reasonable.
That both sides should be operating at the same pace, I agree… I've ranted against what I refer to as a Ferrari versus a Go-kart demonstrations (and training practices) myself a number of times, and my guys get pulled up pretty quickly if they are seen training like that… but I'm not sure where you're getting this idea from… it's actually not seen in the clip itself (there is a related issue, but not that one), and it's not by definition present in paced demo's. Which just brings us back to exactly what you're saying you're frustrated by…
And two. What does this do to the uke? He flinches covers and collapses. Which are not helpful responses. And certainly not something you want to train to be instinctive.
Yeah, you're missing the point here pretty badly as well…
Yes, the attacker (not an "uke"… mind you, if you want to look at the term itself, all it means is "receiver"… so yeah, their job is really to "receive" the technique… which is what's happening) flinches and covers… but why do you think that's not helpful? It's actually very helpful… it's a more realistic response, and entirely appropriate to the overwhelming tactic of Krav Maga, than in many other arts demos… where an attacker comes in with a single attack, then stands as a statue while the defender performs a range of kicks and strikes all over their body.
As far as it not being something you want to train to be instinctive, again, you're really missing the structure and methodology of this training device. Unlike a sporting system, where both sides are trying to employ the same methodology (i.e. it's a matched engagement), this is an attempt to simulate a realistic situation… which is not matched… both sides are employing differing methodologies and tactics… with the idea that the Krav practitioner (the defender) is the one training the technique. The defender (receiver) is there, not to train how to be an attacker, but to provide feedback for the defenders techniques… as a result, covering and flinching is realistic, and is a form of positive feedback provided to the defender, showing that the technique is doing what it's meant to be doing. Which is helpful, if you didn't catch it.
So when you do demos just be normal about it.
That is normal (in the video). But, for fun, how do you define "normal" in this sense? Cause a sporting, resistant, fighting back ideal would be quite abnormal, you know…
I have been guilty of doing this by the way. But have started to think it is a pretty silly way to show a technique.
As I'm still a little unsure of what you're thinking you've been guilty of, or what you think is a "silly way to show a technique", I don't really have a response for this… so I'll simply ask for some clarification.
Are you seeing the issues you are attempting to identify in the clip you linked? The way you've described them, I don't (besides which, if you have an issue with the way things are shown there, you'd really hate my classes…

. I do see a range of issues that I have with the clip, but nothing really close to what you seem to be talking about.
For the record, my issues are that the responses are almost entirely overkill and unnecessary, to the point of being overtly classed as assault in many cases… many of the attacks are "static" (someone holding up a hand, pointing at you, etc), or represent very little actual threat… and garner a response of multiple kicks, including to the head in a number of cases. I also had quite a few issues with the weapon defence (knife, impact, and firearm), with many of them being just shy of suicide to my eyes. The only times I saw something you seem to be discussing was the pacing issue, which was most apparent with some of the bat defences… the attack came in relatively slowly… but that I took as a safety concern with the attack.