I wouldn't presume that this will just get forgotten about. Behaviour like this doesn't go unpunished, and it would be wrong to suggest that it does.
When an officer(s) vandalises a mess or function (and that is what it is effectively) the guilty parties will be hauled in front of the CO and made to pay for the damage in its entirety, that is before any punitive measure is taken in the form of a fine and extra duties. If the individual(s) behaviour is bad enough it can even have consequences on career and promotion.
Let's say in this instance the damage to the projector costs £2000 to put right, the screen another £1000, plus £2000 of damage to fixtures and fittings, that's £5k to be coughed up and usually all in one go! Then comes the fines and other punishments.
The reason that many of the soldiers perceive there to be an imbalance is because they usually get marched in accompanied by the RSM/CSM given a bollocking, and fined before the punishment detail is dished out. If it had been a couple of soldiers found to have caused that amount of damage it would be unreasonable to expect them to be able to stump up £5k in one hit when they earn £13k a year, and so the fines are often only a fraction of the true cost of the damage caused.
The "high spirits" and "Rodney's get away with it every time when soldiers wouldn't" is a myth, ask any of us who have been stuck with the cost of replacing anything whether the damage was caused by a genuine accident or not!