"The purpose of grounding tv/radio antennas is to prevent them from having a neg or pos charge that would attract lightning."
I don't think this is true but am looking for reference material to verify or dispute the concept, not arguing.
When you ground you intentionally make the antenna negatively charged relative to the atmosphere, that charge difference is why lightning wants to find ground in the first place. An ungrounded antenna would seem unlikely to be as negatively charged as a grounded one, if it were positively charged that would make it less attractive to lightning.
"These grounding systems do nothing to dissipate the electricity from a lightning strike, you would need a grounding cable about 6 ft in diameter to even get close."
They do create a path of least resistance which improves your odds of reduced damage to property or personnel. As noted, the cable will be overwhelmed but should help establish an ionized air (ionized = low resistance) path to ground along the way.
You could say that a tall tree does nothing to dissipate 30,000 amps or so of lightning current, but sometimes it does protect lower things in its vicinity by establishing the initial (or one of the initial) paths to ground.