I agree with some of the others experience ranked people use to the rank system. It is a neccessary evil in that you can at a glance know what level of material to start them with. Wheather its a T-shrit or belt or wrist scrap it does give a reference point of where to start. Now there will always be some difference in overall knowledge or skill but there is a reference point.
When I was 1st kyu I could beat lots of Shodan and Nidans even that were fresh from over seas, but they had trained for 2-6 years in a continued curriculum I has trained 4-5 years just at Brown belt (my main teacher was a truck driver) and had 9-10 years of overall training in at least 2-3 various but similar systems. So I would tell them don't feel bad I actually had more time in training then them.
I think its best to see belt rank as a reference point. And I'll add even though I could match or beat some of the Nidans, after sitting down chatting with them I couldn't match their overall knowledge. So rank as mention is more then fighting/sparring its overall knowledge of the system. It doesn't make you walk on water and it doesn't make you superman, it just a reference point of overall skill and knowledge. Some people say that knowledge isn't important but it will be as you go up in rank, it is like any form of education, you are as strong as your foundation.