I'm guessing the drop had less to do with the lowered growth and more to do with them confirming they had to access the equity markets this year when many other companies are avoiding it at all costs.
That is a perfect example of why MPC should not be considered a supportive "sponsor". MPC just wants to rape and pillage, and the sooner the better. I agree 100% with you that the MPLX price decline has everything to do with management stupidity, and management is MPC.
A supportive sponsor would ensure there is no need to access equity capital markets during a period of capital market disruption. I'm just wondering how long it will take for the MPLX yield to equalize with WPZ and ETP, other investment grade MLPs where the market is concerned about opaque (or lack of) disclosures.