There's often a fine line' between wisdom and intelligence; as the saying goes, intelligence is knowing a tomato is a fruit, and wisdom is knowing that you don't put it in a fruit salad. It's often more complicated than that, of course. It's a line that many artists have tried to tread over the years; when they get it right the result can be transformative. Get it wrong and it's at best embarrassing, at worst offensive and inflammatory. Eminem springs to mind as someone whose talent unfettered by wisdom leads him to get it wrong more often than he gets it right.

In that context it seems clear to most intelligent people that there really isn't - or shouldn't - be any topic about which it's wrong to make a joke. Wisdom is knowing when to make a joke and when not to do so; and if so, which joke is appropriate in the circumstances. Ricky Gervais (and other comedians) trumpet freedom of speech tiresomely and repeatedly, illustrating their point with controversial jokes as demonstrating the right to offend. What he so often gets wrong is that said jokes are usually not very funny; and offence for the sake offence just isn't wise or helpful for anyone.

Which brings us to Jojo Rabbit; a light-hearted comedy about a young boy in Nazi Germany, joining the Hitler Youth who has an imaginary best friend. Hitler. Clearly this could go very badly wrong, and it's to writer-director Taika Waititi's credit that he gives himself the role of imaginary-friend Hitler; as a part-Jewish man, it seems fair that if he's going to make this film, he should be the one to take on that role.

It's a mostly comedic, childish Hitler to be sure; but it's still Hitler, occasionally lapsing into the more familiar incarnation of the man we've all come to recognise. Waititi knows comedy, of course; he has a capacity to wring something sweet and funny out of almost anything, a capacity that's on display in this film. The interactions between the boy and Hitler are funny; and the supporting cast of seasoned comedy actors support well, drawing some richly comedic moments out of much of the film. Especially outstanding is Thomasin McKenzie as the Jewish girl hiding in the boy's attic; the boy lives with his mother alone. His sister passed away before the start of the film, his single mother is Scarlett Johansson, in a role that doesn't quite seem properly fleshed out for an actor of her talents.

The first hour zips by, the comedy startling and wise, provoking thought and driving plot; it looks beautiful too. The colours are vibrant throughout, a stark contrast to the usual drabness associated with depictions of wartime Germany and a bold choice; red is everywhere, inescapable and relentless. Around the time we reach the hour mark, the film stutters; the plot keeps moving, but the comedy starts to seem tired, the concept that felt provocative now just feels a little dull. The payoff of the prevalence of the colour red - which should be the film's emotional peak - passed almost unnoticed to me.

All of which left me time to ponder; yes, of course, there were 'good Germans' in wartime Germany. We have many true stories of people who took enormous risks with their own safety to save lives, but the reality was as it always is - the majority were either actively supportive of the regime, or complicit by their silence and passivity. That all Germans here are comedic to greater or lesser degrees starts to feel like glossing over the inconvenient truth that many had blood on their hands; as all we who pay little attention to latent or overt racism, sexism and other prejudices remain and continue to be supportive of it by our inaction or active participation. There are few enough stories that tell these truths - unless, of course, we switch on our news channels and find even a small part of ourselves thinking, 'Don't all lives matter?'.

JoJo Rabbit has things to commend it, but it over-reaches itself; it would be better served as a tight, punchy 45 minutes. In over-reaching, it accidentally gives space to reflect on the film's weaknesses - and our own.