Color me unconvinced.
That's an assumption of bad faith. Now that is something that makes rational discussion impossible. You seem to see yourself as totally above the person talking with you, because you're just "rational". But you continually appeal to emotion yourself, and that emotion is fear:
"it's a slippery slope", "prohibitionists", "using the long arm of the law" (to describe a 5p charge), "regressive", "dangerous question","interminable lists of laws" etc