Pedantic note: whichever side of the Atlantic you dress on, it's always humorous, never humourous. On the other hand that doesn't apply to humourless/humorless. Don't ask me why.
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Myself I'm quite likely to find myself wanting to laugh any time I see someone fall over on the ice, irrespective of whether I think they are good guys or bad guys. Even when I'm sorry for them, say some aspiring athlete in a skating competition. If I thought they were injured, that'd probably stop me.

I was just going to write about that being, at base, a sense of relief that it wasn't me - but then I realised I'd probably find it funny if I fell over and didn't hurt myself. Though of course, there'd be a sense of relief involved in that too.
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That sense of embarrassment at not being an insider, not being in on the joke - what I had in mind was the way that people will quite often make like they are enjoying some bit of social bullying, or some racist joke session, and so forth, when they aren't actually seeing it as funny at all.