The easiest thing to do to make your copper pole safe would be to ground it and disconnect the lights from your house wiring when they aren't in use (if they are plug-in lights and not solar). This article on how lightning rods work is a pretty good explanation of why you do want to ground a tall, conductive pole.
Electricity will travel the path of least resistance to ground. That's why folks working on electric lines have insulating shoes and gloves, but folks working on equipment sensitive to static electricity wear grounding straps. When you're working with high current or potential, you don't want to be the shortest path to ground. When you don't want the sensitive equipment you're working on to be the shortest path to ground, you attach a strap to yourself to provide a better path to ground for any static charge that might accidentally build up.
When lightning strikes, the energy will take the path of least resistance, and has so much power that it can jump small air gaps. If the gap is small enough, and close enough to a good conductor, it becomes the shortest path to ground.
A copper pole is definitely a good candidate for lightning to use as a path to ground, so what you want to make sure of is that the lighting travels completely down the rod to ground, and doesn't jump to, say, the wires of your lights (through their insulation) and travel into your house wiring, frying electronics and generally wreaking havoc. The best way to do that is to ground it properly and make it a sort of lightning rod. It won't "attract" lightning strikes, but if one does occur, it is safer to let it follow the pipe to ground than maybe hit your house.
As an aside, according to a lightning primer from NASA although cloud-to-ground lightning is the most dangerous and damaging, it is the least common.