If it was appropriate, it wouldn't be half as much fun. There's no such thing as inappropriate laughter of course -- laughter is so automatic that that would be like inappropriate breathing. Laughter bubbling up or bursting forth unplanned is a type of honesty. It bursts as a force of nature, not of manufacture. The world needs that safety valve.
Yet, in cartoons or performance, during a speech or at a party, some people do complain that a joke was "inappropriate". Tasteless it may have been, but it has a function: Neitzsche and other philosophers have mentioned the release of tension and the joy of surprise.
It's socially useful to have the ridiculous laughed at (from the Latin ridere, to laugh). It's more than a personal response, it's a social corrective.
When laughter is labelled inappropriate it's usually about sex, gender, race, religion, or something ending in "ism". One person's laughable "ism" is another's no-go area.
Yet laughter goes everywhere; that's why it's powerful. No one has been able to imprison it -- not chilly religions, dictatorial bureaucracy, humorless teachers or anxious parents, no matter how repressive their reactions are. Laughter Laughs Last.
Think of how dangerous the world would be without it. Neitzsche also pointed out is that to oppose a bad idea, laughter is more effective than anger. If we had only anger imagine how much more violent life would be, how full of warfare.
In former ages court jesters were a professional group. In ancient Greece, under the rule of Philip of Macedon they were linked with Court Poets and Philosophers. Likewise in the English Courts of Henry VIII, James VI, and Charles I, where William Summers, Archibald Armstrong and Muckle John performed respectively.
This was reflected in Shakespeare's plays, with their essential Fools. ("Fool", linked to "folly", comes from the Latin noun follis, meaning bellows -- which are full of air and provide oxygen, like humour does.) Being full of air, someone to be jeered at (Shakespeare also dressed characters in ass ears etc.), the Court Fool could say what no one else could, escaping the murderous censors of the time yet managing to tell truths.
Some comics do that today. In their act (or writings or cartoons) they present a farrago of material (a "mixed medley", originally meaning a mixture of fodder: "far-corn").
Humour too is food, for both personal and social nourishment. Spontaneous laughter might erupt when we don't know what to think about something ... and then our subconscious tells us. Conflict is short-circuited, resentment deflected and something else takes the blame ... and escapes. Call it the scape-joke.
