If a person overreacts or gets angry about something, it's probably because there's a grain of truth, sometimes compared to the expression "if the shoe/cap fits"
Darle calabazas a alguien
To give the brushoff
No está hecha la miel para la boca del asno
Don't cast pearls before swine
Llamar al pan, pan y al vino, vino
Plain talking/telling it like it is, sometimes compared to "to call a spade a spade"