You can also use the figurative phrase "take it with a grain of salt," if you adjust the original sentence slightly:
"I heard that pigs fly, but the report was on television, so take it with a grain of salt."
The idiom is defined in Christine Ammer, The American Heritage Dictionary of Idioms (1997) as follows:
with a grain of salt Also, with a pinch of salt. Skeptically, with reservations. For example, I always take Sandy's stories about illnesses with a grain of salt—she tends to exaggerate. This expression is a translation of the Latin cum grano salis, which Pliny used in describing Pompey's discovery of an antidote for poison (to be taken with a grain of salt). It was soon adopted by English writers.