The LCD symbol has likely tagged the anode pin of the backlight as a "input power", explaining the warning/error.
I do not recommend that - generally speaking diode pins should just be tagged "passive" IMO.
But as a more general rule, the idea is that KiCad doesn't know that whatever net is after a resistor, even if said resistor has its other end connected to an "output power", is also an "output power". And it sort of makes sense, as ERC is a pretty basic rule check and is not meant to analyze your circuits and if they are designed properly.
So here, to silence the error, you can either just set it as an exception in KiCad and not change anything - it will not come back. Or, you can modify the symbol to set the anode pin as passive. Or, you can attach a 'PWR_FLAG' to the net between the resistor and the anode, which is how it's usually done.