Moral panic is when you have a democratic body enter a state of agitation over a situation and demand immediate legislative action to fix it. This doesn't need to be a momentary thing, but typically it involves a well-supported movement that gathers political steam to force the hands of legislators into acting.
A satirical instance that illustrates this well happens in the musical The Music Man. Professor Harold Hill comes to River City, Iowa and induces a moral panic over the new pool hall, by claiming that gamblers will soon invade their town and corrupt their youth. He then suggests that the town needs a band instead (and it just so happens he sells the instruments).
The problem with moral panics is that the laws are often crafted hastily, without regard for how they will be used.
A real life version of a moral panic was the spate of laws passed to register sex offenders so that the handful of tragic cases involving repeat offenders would not happen again. The problem is that these laws were often written when most child exploitation involved simple child pornography or rape (things most people still agree are bad). Many of these laws did not conceive of a day when teens with smartphones would technically produce child porn... of themselves. As such, some poorly written state laws can charge teens for "victimizing" themselves
When he was 17, E.G. sent a text message with a photograph of his erect penis to a young adult woman he knew through his mother. The woman reported the incident to police, and the prosecutor chose to charge E.G. with the felony sex offense of dealing in depictions of a minor engaged in sexually explicit conduct — a law typically used to prosecute child pornographers.
That’s right: E.G. was named as both the perpetrator and the victim of the crime of child pornography. He was convicted and required to register as a sex offender after the trial court rejected a motion to dismiss for insufficient evidence.
Bestiality doesn't seem to fit here. Many laws prohibiting sex were passed during a time when society was in tighter agreement about having laws enforce general morality. While laws like that might not get passed today, there's also not much impetus to remove them either.