You could even just cut to the chase and call the person themselves a placebo, which, according to the OED, meant " a flatterer, a sycophant, [or] a parasite."
" I understand, " said Stanislas, " it's like the crow who is silly enough to let his cheese fall and be taken by the fox who has been playing the flatterer" .
An anti-Semite like his father, and a hater of Asians to boot, Nicholas the Second developed the bad habit of listening only to those people he thought worthy, his wife Alexandra and the circle of court flatterers.