Royal Navy raids on enemy coastal shipping

Was the Royal Navy sometimes a coast-defence navy protecting enemy coastlines from their owners' shipping?

The joke is accepted as a description of its attacks on French coastal shipping during the Napoleonic Wars.

Calling the Royal Navy a force that protected enemy coastlines from their own shipping is accepted as a joke about the Napoleonic Wars. Its historical point is the Royal Navy's willingness to seize vessels moving along the French coast. The language of protection is ironic, referring to taking enemy shipping as prizes.