S’dei Chemed has a long piece defending the recital of Machnisei Rachamim.
http://hebrewbooks.org/pdfpager.aspx?req=43519&st=&pgnum=6&hilite=
As HaLeiVi points out, the Mahara”l had two ways of defending it; although his conclusion is not to say it, he clearly would not consider someone who does say it to be in violation of the principle recorded by the Ramba”m.
Charlie is completely off base here.