Disrespectful? Not at all.
Half a century ago, challenge matches called "Beimo" were an honored tradition in Chinese martial arts. These were bare-knuckle "skill comparison" matches with few or no rules (but usually a consensus on when a fight was over; according to WSL at least, the "ground and pound" you see in MMA didn't really happen.) The main purpose of these matches was for martial artists to learn to use their arts in an entirely realistic, combative setting. However, it also kind of helped to filter out bad schools, as when a student of one school defeated the teacher of another, that teacher's school tended to lose its reputation. A number of very humble, and highly respected figures in my art (Wing Chun) were famous for their challenge matches.
Personally, I think we have too much an aversion to what we percieve as "violence" these days, and too much emphasis on pure "self defense." Someone who has never used his art in a truly combative sense still does not understand it; and if two people accept the prospect of getting beaten up to learn and better understand their arts, I don't really see anything wrong with that as long as they still conduct themselves in a civilized manner.
EDIT: I should probably point out, however, in the context of today's day and age, there are serious legal issues to consider here, so I would not recommend challenging another school to this kind of match for that reason alone. I'm more just expressing the sentiment that it's somewhat unfortunate that it doesn't happen any more, so a lot of frauds and under-qualified people get away with teaching without ever being put to the test.
If, however, you can organize a match using gloves, and in a safe and legal environment, I don't see anything wrong with that.