Same thing here. Charged me $75 to enroll Corporate Card in MR. I actually received a letter from some VP at Amex explaining how they were trying to align all rewards programs.

Alignment my foot, I immediately cancelled the Platinum card, redeemed 140,000 MR points, downgraded Amex Corporate to Membership Rewards Options ($40) and shifted 90% of my spending to Starwood and Hilton Amex. Greedy pigs...