MIT's not good for tube components?

I was at a hi-fi store the other day and started chatting with the owner regarding improving my system and such. We got to the subject of cables, and I mentioned that I was using MIT 2 biwire for speaker cables and MIT 330 shotguns for IC's. He quickly mentioned that I needed to get new cables, because MIT's weren't good for tube components. I wasn't sure if he was trying to get me to buy cables from him or if in fact MIT's are deficient for tube components.

Any comments regarding this?

Also, if you have any recommendations for speaker cables and IC's that may mate well with my system, I would appreciate them.

My system:
Vandersteen 2ce sig
Eastern Electric Minimax tube CDP
TAD-150 sig tube preamp
McCormack DNA-1 deluxe