Answer:
In the provided excerpt, the sentence that gives a counterclaim is:
"People under age 18 don't have the same rights, or responsibilities, as full-fledged adults."
This sentence presents a counterargument to the proposed law change by pointing out that teenagers have different rights and responsibilities compared to adults, implying that they may need some level of government intervention.
The other sentences in the excerpt support the author's viewpoint in favor of the proposed law change, arguing for government intervention to protect young people from harmful beverages and suggesting that rules should evolve with the times.