Some people consider CAPM to be one of the outcomes of MPT.

Harry Markowitz delivered this rebuke of CAPM in 2005: http://www.q-group.org/wp-content/uploads/2014/01/Markowitz2.pdf .

Could it be that CAPM is a tautology? "Given that all investors have the same views and preferences, all investors would hold the market portfolio."

But then of course, you knew that equilibrium cannot actually exist in a capital market because trading would cease -- refer to http://alex2.umd.edu/wermers/ftpsite/FAME/grossman_stiglitz_(1980).pdf