While satyrs usually get a pretty bad rep in Classical mythology, the satyrs in the Faerie Queene come off relatively well. They're pretty much benign and even help Una out when Sansloy is chasing her. Where they go wrong is in the religion.
While they recognize Una's beauty and holiness—their leader Sylvanus is totally stunned—they mistakenly start to worship her instead of what she stands for, i.e. Christian belief and Jesus. By turning her into a literal manifestation of a goddess, they are making the mistake Christians believes all polytheistic religions made in worshipping objects they can see instead of Divine truth that they can't. Just to make sure you totally appreciate their silliness, once the satyrs stop worshipping Una they start worshipping her donkey.