Personally, I'm not against enforcement of leash laws. But, just for some context: it's an area GGNRA has only just taken over this month, which has previously functioned as a local park with little enforcement. GGNRA's dog policy is still under review and the sudden clamp down really took locals by surprise.
IMO, the ranger would have done much better to take some time to introduce herself to all the locals walking by, issue warnings for infractions, and ask the locals to spread the word that National Park Rangers, who are federal law enforcement officers, will be handing out expensive tickets and detaining people if necessary.
He definitely did some things wrong, but a taser is potentially deadly force and should be reserved for truly dangerous situations -- not someone walking away from a ticket for a minor infraction.