Goats eat anything.
Occasionally unwisely.
I have it on good authority that this is an old wive's tale.
They are actually quite picky about what they eat...
They eat anything. They eat your clothing if you stand still for too long, they eat almost any vegetation. They also have a digestion that can cope.
There are companies in the USA making use of this to eliminate invasive species, nice vid about it on bbc last week.