What's a word for someone who presents their negative opinion as if it's someone's else?

Solution 1:

deflect

  1. draw someone's attention away from something

Edit:

A couple more have come to mind. The manager may be said to be "feigning impassivity", or the manager may be "dissembling", although the latter is admittedly a more general term that may not fit the specificity the OP is asking for.