Ah yes, truly a great achievement and there is no shame in losing to one of the P4P greats Brad Pickett. Just look at the list of BW fighters MM has beaten - Miguel Torres and Kid Yamamoto, two fighters that were still in their prime when he fought them, the one and only Marshall Carlyle and the always prepared Eric Alvarez. To top it off, MM fought Cruz for the title (and lost by UD).
[1] Seriously, MM is a truly talented guy but if you think bringing up his BW career as any type of proof that he challenged himself you're delusional. He has been mostly fighting nobodies and had two wins in the UFC before his title shot against Cruz that were against two formerly good fighters who at the time were a shell of their former selves. There is absolutely nothing impressive at all with his BW career and he fought his way to a title shot when the division was thin.
[2] MM should do whatever he wants - if he's happy with defending his title against "elite" fighters like Borg and Reis, then he should do it. I respect the guy as a person, seems like a super nice guy, but [3] if he wants to gain fans, fame, money and recognition it wouldn't hurt if he jumped on the opportunity to challenge himself.