I have never done or seen any actual tests reports on this but everything that I have heard is completely to the contrary.

I just searched around a little about it and I find that it actually has good corosion resistand properties. This stuff (molybdenum disulfide) is used in everything from bullets to the space industry. It has an operating pressure limit of well over 250,000 psi. It is said to be able to work into small scraches and such to aid lubrication even further.

I think that your salesman is full of crap.