Town councillor: The only reason for the town to have ordinances restricting where skateboarding can be done would be to protect children from danger.
Conclusion
The town should not pass an ordinance prohibiting skateboarding in River Park.
Evidence
The only reason for the town to restrict skateboarding would be to protect children from danger. Park skateboarding is dangerous, but if banned, children will skateboard in the streets. Street skateboarding is more dangerous than park skateboarding.
Evaluate
The author is saying that since the whole point of the ordinance would be to protect children from danger, we should prohibit skating in the park because that will lead skaters to do something even more dangerous: skate in the streets.
Goal
Let's look for something like,
If the answer isn't set up as a rule that would lead us to conclude, "Shouldn't pass the ordinance", then we shouldn't give it more than a glance on a first pass.