It is not that the 14 AWG wire will zap you. Properly insulated (just the original insulation, no need for extra tape) will protect you from being zapped.
The concern is heat, because heat leads to fires. A 14 AWG will heat up more than a 12 AWG wire, and if that wire is inside insulation and at a full 1500W then it could be a problem.
But, you may say, I am only using it for 50W of LED lighting? That's true now.
But the next owner (we see it all the time) will ask about connecting a receptacle in the same box. But wait, they may say, I only want to use it for plugging in phone chargers (low wattage, minimal heat).
But the next owner will see the receptacle and decide to plug in a space heater when the furnace is on the blink. Oops, two space heaters because it is a duplex receptacle. That's 24A - 2 x 12A - because a standard US space heater, with or without a fan, ceramic, oil-filled, whatever, uses 12A = 1500W (based on 125V).
24A = 120% of 20A (the circuit breaker) but 160% of 15A (what you should have for 14 AWG wire).
Take a look at a trip curve
Hard to tell exactly, and it is a range because of manufacturing tolerances, aging, etc. But basically it shows that at 120% you could get a trip from anywhere between 100 seconds, which would be fine, and never. The wire sizing rules factor this in - everyone knows a 12 AWG wire could handle a bit more than 20A and a 14 AWG wire could handle a bit more than 15A, but there are limits for a reason.
Now look at 160% (1.6 on the chart - i.e., a bit past 1.5). You get a trip somewhere between 20 seconds and 2 minutes. So on a 15A breaker, that double space heater on 14 AWG wire will trip the breaker in enough time to prevent a fire. On a 20A breaker it might not ever trip, even with everything functioning properly.
And that's how houses burn down.