Marijuana potency is apparently variable

The latest scare story about marijuana is that, once again, some pot is apparently more potent than other pot: Marijuana potency surpasses 10 percent, U.S. says.
This causes all the usual suspects to act concerned, as if this was something bad, yet at the same time, none of them would even consider a proposal to label pot by its potency. You’d think that would be the logical reaction. Or even regulating potency. But no, not a word.
Apparently potency is a big deal. Let’s take a quick review of potency:

• Beer: 4-7 percent potency
• Pot: 10 percent potency
• Wine: 11-13 percent potency
• Distilled Spirits: 40 percent potency
• Bacardi 151: 75 percent potency
• Marinol: 100 percent potency

(*Your grandfather’s pot: negative 5 percent potency, apparently, if you believe government officials)
Government officials discovered something else pretty remarkable:

The stronger marijuana is of particular concern because high concentrations of THC have the opposite effect of low concentrations, officials say.

I’m a little confused by this. Are they saying that high concentrations of THC make you no longer like Doritos? Or perhaps that it makes you prefer Debby Boone over Pink Floyd? I have no idea.