Not sure but think you may have misunderstood the point. The respect should be there for your sempai from the get go. That way you don't get into a pickle, like 5th kyu's handing out advice to 2nd kyu's. This etiquette is inherent in the Japanese social hierarchical system. And although we are not Japanese nor are we attempting to become, it does lend itself to creating a well ordered and structured learning environment. Which is for the betterment of all deshi.
A sempai will not correct a student for not showing them respect, they don't have to, the instructor has taken care to ensure that everybody understands the correct etiquette from the get go.
Once again, I see nothing wrong with a 5th kyu giving advice to a "sempai"? If you have this person pinned for ikkyo, and it is loose enough for their shoulder to turn out of it, wouldn't you like them to let you know you need to move their arm that extra half inch?
In my mind, that slows down progress for both the sempai and the kohai. It would be great if one could wait for the instructor to come over and offer pointers, but honestly, if you have 6 pairs practicing on the matt, that isn't going to happen very often.
I would also argue that by encouraging our kohai to critique us, it encourages them to think critically about the techniques and not drift into that "if I just do it 50,000 times, it will somehow become good."
That being said, if one feels there is abuse on the matt, then it is important to talk to that person about it off the matt, and if that isn't effective, have a conversation with the dojo-cho about it.